EADV Task Force Pruritus White Paper on chronic pruritus and chronic prurigo: Current challenges and future solutions

Chronic pruritus (CP) is frequent in general medicine and the most common complaint in general dermatology. The prevalence of CP is expected to rise in the future due to the ageing population. The clinical presentation, underlying aetiology and treatment strategy of CP are heterogeneous. Also, individual treatment aims and physical, psychic and economic burdens of patients might vary. Chronic prurigo (CPG) is the most severe disease in the chronic pruritus spectrum, being associated with long-standing scratch-induced skin lesions and a therapy refractory itch-scratch-cycle. It is thus important to raise disease awareness for CP and CPG in the general public and among decision-makers in the health system. Further, there is a need to support a rational clinical framework to optimize both diagnostics and therapeutics. Currently, there is still a shortcoming regarding approved therapies and understanding CP/CPG as severe medical conditions. Therefore, the EADV Task Force Pruritus decided to publish this white paper based on several consensus meetings. The group consented on the following goals: (a) ensure that CP is recognized as a serious condition, (b) increase public awareness and understanding of CP and CPG as chronic and burdensome diseases that can greatly affect a person's quality of life, (c) clarify that in most cases CP and CPG are non-communicable and not caused by a psychiatric disease, (d) improve the support and treatment given to patients with CP to help them manage their disease and (e) publicize existing therapies including current guidelines. We aim to point to necessary improvements in access and quality of care directed to decision-makers in health policy, among payers and administrations as well as in practical care.

Google search trends for itch in Europe: a retrospective longitudinal study

BACKGROUND

Itch is a common symptom in the general population. Affected individuals often do not seek medical consultation and rely on Internet searches to obtain information regarding their itch.

OBJECTIVES

The aim of this study was to attain insights into common concerns of the general population regarding itch can by analysing itch-related Internet search behaviour.

METHODS

Google AdWords Keyword Planner was used to assess search volumes for itch-related terms in 15 European countries between September 2014 and August 2018. All identified keywords were qualitatively categorized. Itch-related terms were descriptively analysed and are shown as number of searches/100 000 inhabitants.

RESULTS

The search volume for the keyword 'itch' per 100 000 inhabitants was highest in Northern Europe, followed by Eastern, Central and Southern Europe. In 4/15 countries, itch was searched for more often in the autumn/winter months compared to in the spring/summer months. Most itch-related terms were related to dermatological conditions such as inflammatory skin diseases (e.g. psoriasis, atopic dermatitis), allergic or immunologic conditions (e.g. urticaria), and infectious diseases or infestations (e.g. scabies). In terms of body location, genitoanal itch dominated the searches. Symptoms and signs related to itch, possible non-dermatological aetiologies, and treatment options were also among the most searched terms.

CONCLUSIONS

These analyses provided for the first time insights into the search behaviour patterns related to itch across Europe. People from Northern and Eastern Europe are more likely to seek online information regarding itch. Causes for the itch, especially dermatological conditions, and genitoanal itch are the most important concerns for Internet users. This unconventional and inexpensive method identifies medical needs of people beyond the medical setting, including people who do not seek medical consultation. Accordingly, the data could be used to guide public health interventions and manage respective inhabitants' medical needs.

Chronic nodular prurigo: clinical profile and burden. A European cross-sectional study

BACKGROUND

Chronic nodular prurigo (CNPG) is a condition characterized by chronic itch, a prolonged scratching behaviour and the presence of pruriginous nodules. A comprehensive understanding of this condition, especially regarding its clinical characteristics and impact on quality of life is still lacking.

OBJECTIVES

Aim of this pan-European multicentre cross-sectional study was to establish the clinical profile of CNPG, including its associated burden.

METHODS

Fifteen centres from 12 European countries recruited CNPG patients presenting at the centre or using the centres' own databases. Patients were asked to complete a questionnaire in paper or electronic format. Demography, current co-morbidities, underlying disease, itch intensity, additional sensory symptoms, quality of life, highest burden and emotional experience of itch were assessed.

RESULTS

A total of 509 patients (210 male, median age: 64 years [52; 72]) were enrolled. Of these, 406 reported itch and CNPG lesions in the previous 7 days and qualified to complete the whole questionnaire. We recorded moderate to severe worst itch intensity scores in the previous 24 h. Scores were higher in patients with lower educational levels and those coming from Eastern or Southern Europe. Most patients experience itch often or always (71%) and report that their everyday life is negatively affected (53%). Itch intensity was considered to be the most burdensome aspect of the disease by 49% of the patients, followed by the visibility of skin lesions (21%) and bleeding of lesions (21%). The majority of patients was unaware of an underlying condition contributing to CNPG (64%), while psychiatric diseases were the conditions most often mentioned in association with CNPG (19%).

CONCLUSIONS

This multicentre cross-sectional study shows that itch is the dominant symptom in CNPG and reveals that the profile of the disease is similar throughout Europe.

Position Statement: Linear prurigo is a subtype of chronic prurigo

BACKGROUND

Chronic prurigo (CPG) is a distinct disease characterized by chronic pruritus, history and/or signs of prolonged scratching and multiple pruriginous lesions. It may present with various clinical manifestations, including papules, nodules, plaques or umbilicated lesions. Some patients with chronic pruritus show pruriginous linear and scaring scratch lesions (LSSL) and it is unclear whether these lesions belong to the spectrum of CPG.

OBJECTIVE

To achieve a consensus on the classification of pruriginous LSSL and establish criteria to differentiate them from similar appearing conditions of different nature.

METHODS

Members of the Task Force Pruritus (TFP) of the European Academy of Dermatology and Venereology participated in the consensus conference, discussing representative clinical cases. Using the Delphi method, consensus was reached when ≥75% of members agreed on a statement.

RESULTS

Twenty-one members of the TFP with voting rights participated in the meeting. It was consented that LSSL occurs due to chronic pruritus and prolonged scratching, and share common pathophysiological mechanisms with CPG. LSSL were thus considered as belonging to the spectrum of CPG and the term 'linear prurigo' was chosen to describe this manifestation.

CONCLUSION

Considering linear prurigo as belonging to the spectrum of CPG has important clinical implications, since both the diagnostic and therapeutic approach of these patients should be performed as recommended for CPG. Importantly, linear prurigo should be differentiated from self-inflicted skin lesions as factitious disorders or skin picking syndromes. In the latter, artificial manipulation rather than pruritus itself leads to the development of cutaneous lesions, which can show clinical similarities to linear prurigo.

Therapeutic and experimental therapeutic studies on acupuncture and itch: review of the literature

Itch accompanies most inflammatory skin diseases but may occur as a solitary sensation in otherwise normal skin. Chronic itch often requires combined treatments but some cases remain therapy resistant. Complementary medicine is becoming increasingly popular among patients. Acupuncture is the oldest and most well-studied alternative option with evidence-based effect on pain. This article summarizes the rational for the use of acupuncture in treatment of itch and reviews therapeutic and experimental therapeutic studies on acupuncture and itch.

Cutaneous innervation before and after one treatment period of acupuncture

BACKGROUND

The effect of acupuncture on nociceptive pain is well documented, but effects on nociceptive itch have been contradictory.

OBJECTIVES

To evaluate possible effects of acupuncture on the occurrence, distribution and function of sensory nerve fibres in human skin.

METHODS

Ten subjects were treated by inserting 10 acupuncture needles subcutaneously at the upper lateral aspect of one buttock. The subjects were recruited from an acupuncture clinic and were undergoing specific acupuncture treatment for their disorders. The needles were stimulated (rotated to and fro) twice during the twice-weekly 25-min sessions over 5 weeks. Skin biopsies, diameter 3 mm, were taken before and 3-6 days after local acupuncture. Antibodies to the pan-neuronal marker protein gene product 9.5 (PGP 9.5), calcitonin gene-related peptide (CGRP), vanilloid receptor 1 (VR1) and mu- and delta-opioid receptors were employed to study sensory unmyelinated nerve fibres that transmit nociceptive pain and itch. A histamine prick test using planimetry was used to record experimental itch after acupuncture on the treated area and on the corresponding control skin, and a visual analogue scale was used to evaluate itch.

RESULTS

The mean +/- SEM number of CGRP-immunoreactive nerve fibres per biopsy section was reduced from 36.0 +/- 3.3 to 21.3 +/- 4.0 (P = 0.05) after the treatment. PGP 9.5-immunoreactive nerve fibres were found both in the epidermis and in the subpapillary dermis. The mean +/- SEM total number of PGP 9.5-immunoreactive nerve fibres decreased from 249.8 +/- 16.7 to 211.8 +/- 12.0 (P = 0.03). The PGP 9.5-immunoreactive nerve fibres occurring in the dermis appeared more fragmented after the acupuncture compared with pretreatment. VR1 immunoreactivity was found both in the free nerve fibres and in kite-like formations, possibly mast cells, throughout the dermis, sometimes occurring around hair follicles. The mean +/- SEM number of VR1-immunoreactive elements was not significantly influenced by acupuncture, at 33.5 +/- 4.6 vs. 43.0 +/- 4.4 (P = 0.09). No immunoreactivity was found in the skin against mu- and delta-opioid receptors with the antibodies used in this study. Neither histamine-induced itch nor cutaneous responses were influenced by acupuncture.

CONCLUSIONS

The present data indicate an effect of acupuncture on neuropathic itch but not histamine-mediated itch. Our findings support the opinion that the pain-relieving effects of acupuncture partly depend on its effect on the peripheral innervation.

Circulating eosinophils in asthma, allergic rhinitis, and atopic dermatitis lack morphological signs of degranulation

BACKGROUND

In allergic diseases, eosinophils in affected tissues release granule proteins with cytotoxic, immunoregulatory, and remodelling-promoting properties. From recent observations, it may be assumed that eosinophils degranulate already in circulating blood. If degranulation occurs in the circulation, this could contribute to widespread systemic effects and provide an important marker of disease.

OBJECTIVE

To determine the degranulation status of circulating eosinophils in common allergic diseases.

METHODS

Using a novel approach of whole blood fixation and leucocyte preparation, the granule morphology of blood eosinophils from healthy subjects, non-symptomatic patients, symptomatic patients with asthma, asthma and Churg-Strauss syndrome, allergic rhinitis, and atopic dermatitis was evaluated by transmission electron microscopy (TEM) and eosinophil peroxidase (TEM) histochemistry. Plasma and serum levels of eosinophil cationic protein were measured by fluoroenzymeimmunoassay. Selected tissue biopsies were examined by TEM.

RESULTS

Regardless of symptoms, circulating eosinophils from allergic patients showed the same granule morphology as cells from healthy subjects. The majority of eosinophil-specific granules had preserved intact electron-density (96%; range: 89-98%), while the remaining granules typically exhibited marginal coarsening or mild lucency of the matrix structure. Abnormalities of the crystalline granule core were rarely detected. Furthermore, granule matrix alterations were not associated with any re-localization of intracellular EPO or increase in plasma eosinophil cationic protein. By contrast, eosinophils in diseased tissues exhibited cytolysis (granule release through membrane rupture) and piecemeal degranulation (loss of granule matrix and core structures).

CONCLUSION

In symptomatic eosinophilic diseases, circulating blood eosinophils retain their granule contents until they have reached their target organ.

Familial brachioradial pruritus

BACKGROUND

The cause of brachioradial pruritus (a localized itching on the arms or shoulders) is controversial. A hereditary form of this condition has not been reported.

OBJECTIVES

To describe the occurrence of brachioradial pruritus in several members of one family.

PATIENTS AND METHODS

The pedigree of the three generations and the history of brachioradial pruritus was outlined. Four sisters were investigated by radiography of the cervical spine.

RESULTS

Five sisters and one brother, together with five of their daughters suffered from recurring brachioradial pruritus. The sisters had had occupations requiring heavy lifting, spent much time outdoors and exposed themselves extensively to the sun. Several complained of neck pain and cervical radiographs of four of them indicated arthrosis.

CONCLUSIONS

Spinal disease alone cannot explain the symptoms of brachioradial pruritus, which in our patients was characterized by symptom-free periods broken off by relapse late in the summer each year. The pedigree suggests this hereditary form of brachioradial pruritus to be dominant and possibly X-linked.

Cutaneous field stimulation of sensory nerve fibers reduces itch without affecting contact dermatitis

BACKGROUND

A new technique, cutaneous field stimulation (CFS), which activates electrically unmyelinated C-fibers, is used to treat localized itch. Its action is similar to that of capsaicin, the pungent agent in hot peppers, which enhances delayed allergic reactions. The aim of the study was to investigate how experimental contact dermatitis responds to CFS.

METHODS

Twelve patients with contact dermatitis in response to nickel were treated by CFS for 1 h each for four consecutive days. A flexible plate containing electrodes was applied to a test area on the upper arm and was stimulated by a constant current (0.8 mA). On the fifth day, patients were provoked by epicutaneous application of nickel sulfate (allergic contact dermatitis) and benzalkonium chloride (irritant contact dermatitis), and by intradermal tuberculin (delayed immunologic reaction). Twelve other patients with IgE-mediated allergy were treated by CFS on the lower arm for 1 h and were then pricked with histamine and allergen extracts (wheal volume was measured) and were tested using benzoic acid (nonimmunologic contact urticaria; closed test). Ten of these patients were also treated by CFS for four days, and experiments were performed on the fifth day.

RESULTS

Test reactions to nickel, benzalkonium, and tuberculin were found to be unaffected by CFS treatment. Although allergic prick test reactions were enhanced (by 28%) after a single CFS treatment, the associated itch was significantly reduced both after single and repeated CFS treatments (by 65% and 38%, respectively).

CONCLUSIONS

Repeated use of CFS to reduce itch has no adverse effects on contact dermatitis.

Cutaneous field stimulation in the treatment of severe itch

OBJECTIVE

To evaluate the efficacy of cutaneous field stimulation of C fibers for the treatment of itchy skin and its effect on peripheral nerve fibers as shown in skin biopsy specimens.

DESIGN

We conducted an open-label uncontrolled study of 19 patients with itching. Each patient applied a flexible plate containing electrodes to the itchy area for 20 minutes at a time once daily for 5 weeks to stimulate nerve fibers with a constant current (0.8 mA). Skin biopsy specimens were collected before treatment and at the end of treatment and were immunostained for calcitonin gene-related peptide and protein gene product 9.5.

SETTING

University hospital in Lund, Sweden.

PATIENTS

Sixteen patients with nostalgia paresthetica or brachioradial pruritus and 3 with generalized itch.

INTERVENTIONS

Cutaneous field stimulation and punch biopsies of the itchy skin.

MAIN OUTCOME MEASURES

Visual analog scale for assessment of itching and counting the immunoreactive nerve fibers in 3-mm biopsy specimens.

RESULTS

Patients with localized itching experienced a reduction in mean values on the visual analog scale (from 78% before treatment to 42% by the end of the fifth week). The number of protein gene product 9.5- immunoreactive nerve fibers in the epidermis was reduced by 40% by the end of treatment compared with baseline values.

CONCLUSIONS

Cutaneous field stimulation is an effective alternative for the treatment of localized itching. The reduction in itching is accompanied by degeneration of the epidermal nerve fibers, as evidenced by the loss of protein gene product 9.5 immunoreactivity.

Nitric oxide participates in prick test and irritant patch test reactions in human skin

The aim of this study was to investigate the involvement of nitric oxide (NO) in the modulation of immediate and delayed immunological and nonimmunological reactions in human skin. The NO donor nitroglycerin, 0.1 microgram, and the NO synthase inhibitor, NG-nitro-L-arginine (L-NAME), 0.1 microgram, were injected intracutaneously prior to provocation tests. The following provocation tests were carried out: 8 patients with pollen allergy to birch were provoked by a prick test with the allergen and the volume of the weals was measured; 20 patients with allergy to nickel were provoked with nickel sulfate epicutaneously; and 26 healthy volunteers were provoked with tuberculin (causing delayed immunologic reaction), benzalkonium chloride (irritant contact dermatitis), UV radiation or benzoic acid (nonimmunological contact urticaria). The test reactions were evaluated by planimetry. L-NAME inhibited irritant contact dermatitis (P = 0.020) but augmented immediate immunological reactions (prick test) (P = 0.016). The other test reactions remained unchanged. Nitroglycerin did not affect any of the reactions significantly. The results suggest that NO is involved in immediate immunological reactions and irritant contact dermatitis.

Dual effects of CGRP-antagonist on allergic contact dermatitis in human skin

There is increasing evidence of an interaction between the nervous and the immune systems. The aim of this study was to investigate the rôle of calcitonin gene-related peptide (CGRP) in the modulation of the elicitation of immediate and delayed, immunological and non-immunological reactions in human skin. CGRP (13 pmol and 39 pmol), and the CGRP-antagonist, CGRP/8-37/, (50 pmol and 500 pmol) were injected intracutaneously prior to provocation tests. Patients with allergy to nickel were provoked with nickel sulfate epicutaneously, and the reactions were evaluated by a clinical scoring system (guidelines of the International Contact Dermatitis Research Group). Patients with allergy to birch pollen were provoked by a prick test with the allergen, and the volume of the weals was measured. The patients were also provoked with tuberculin (delayed immunologic reaction), benzalkonium chloride (irritant contact dermatitis), UV-light and benzoic acid (non-immunologic contact urticaria). The test reactions were estimated by planimetry. CGRP/8-37/ exerted dual effects on allergic contact dermatitis, causing potentiation at a dose of 500 pmol (p= 0.004) and inhibition at a dose of 50 pmol (p=0.012). Other reactions were not significantly affected by the pretreatments. The results suggest that CGRP participates in delayed inflammatory reactions, but is not involved in immediate immunologic reactions.

Neuropeptide-containing C-fibres and wound healing in rat skin. Neither capsaicin nor peripheral neurotomy affect the rate of healing

Wound healing in rat skin was studied in standardized wounds inflicted on both hind legs after unilateral sciatic nerve sectioning and/or capsaicin-induced depletion of sensory nerve (C-fibre) neuropeptide content. Daily visual inspection, histological examination and immunohistochemistry with antibodies against substance P, calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide, neuropeptide Y and a pan-neuronal marker, protein gene product 9.5 (PGP 9.5) were used to assess wound healing and determine the distribution of dermal nerve fibres. In controls, nerve fibre density in the wound tissue was low during the first few days after wound infliction, but started to increase on day 4, reaching a peak on day 7 when 25% of medial wounds and 70% of lateral wounds were healed. All wounds were healed on day 11, a scar appearing on day 14 followed by a decrease in nerve fibre density. Capsaicin treatment and/or sciatic nerve sectioning reduced the density of CGRP-immunoreactive nerve fibres by 70% and that of PGP 9.5-immunoreactive fibres by 50%. The capsaicin-induced reduction in PGP 9.5-immunoreactive nerve fibre density is attributable to partial destruction of peripheral nerve fibres. CGRP-immunoreactive and PGP 9.5-immunoreactive nerve fibre density was restored both in capsaicin-treated and denervated groups, reaching a maximum, corresponding to the original level, by days 4-10. Neither the reduction in nerve fibre density following sciatic nerve sectioning nor the impairment of sensory nerve functional capacity following capsaicin treatment affected the rate of wound healing, all wounds being closed on day 11. The study shows that it is difficult to knock out all cutaneous sensory innervation. Thirty per cent of C-fibre innervation seems enough to ensure a normal wound healing.

Vasoactive peptides in the skin

The vascular effects of endogenous substances can be easily studied in the skin. Early in this century, vasoregulation was shown to be dependent on innervation. Peptidergic transmitters have been shown to co-exist and co-transmit along with nonadrenalin and acetylcholine, sometimes being responsible for nonadrenergic-noncholinergic responses. This review summarizes recent information on vasoregulatory effects of neuropeptides such as substance P (SP), neurokinin A (NKA), calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide (VIP), pituitary adenylate cyclase activating peptide (PACAP), neuropeptide Y (NPY), and somatostatin. All these peptides are vasodilators, and some of them seem to be involved in neurogenic inflammation. Some vasoactive peptides and other vasoactive molecules, such as nitric oxide (NO) and histamine, can originate both from nerves and cells and are crucially involved in vasoregulation. Other cell-derived peptides and molecules, such as bradykinin, endothelins, and prostaglandins, may contribute to neurogenic inflammation. All the peptides and molecules described also exist in other organs such as the brain, heart, lung, pancreas, and gastrointestinal tract. The effect of neuropeptides seems to vary from one organ or tissue to another, e.g., NPY is a potent vasoconstrictor in cardiac and cerebral vascular beds but acts as a vasodilator when it occurs in the skin. The presence of mast cells and inflammatory cells may create a special environment in the skin.

Occurrence and distribution of peptidergic nerve fibers in skin biopsies from patients with systemic sclerosis

Systemic sclerosis is characterized by vascular dysfunction. Itch is sometimes present in early stages of the disease. This prompted us to study the innervation of the skin by immunocytochemistry. Antibodies to neuropeptide Y and vasoactive intestinal peptide were used for autonomic nerves. Sensory innervation was studied using antibodies to substance P and calcitonin gene-related peptide. Protein gene product 9.5 was used as a general neuronal marker. Skin biopsies from affected (lower arm) and non-affected (upper back) sites on 10 patients with systemic sclerosis and from corresponding sites on 10 sex- and age-matched healthy controls were studied. Regional variations were found in the occurrence of peptidergic nerve fibers. In the patients the density of nerve fibers (measured semiquantitatively) stained by the panneuronal marker was lower in affected than in unaffected skin (p < 0.05). There were no significant differences in peptidergic innervation between patients and controls. However, there was a tendency to higher density of neuropeptide Y-positive nerve fibers in the forearm skin in 6 to 10 patients, as compared to only 1 of 10 healthy controls.

Innervation of the skin of the forearm in diabetic patients: relation to nerve function

Complications of diabetes include sensory and autonomic neuropathy. The aim of the present paper was to study the degree of sensory and autonomic neuropathy and correlate these findings with the distribution and density of neuropeptidergic nerve fibers in the skin of the forearm of diabetic patients and healthy controls. We investigated 30 diabetics (24 type 1 and 6 type 2) and compared them with 13 healthy controls. There were no differences between the groups with respect to density and distribution of nerve fibers displaying immunoreactivity to the pan-neuronal marker PGP 9.5 and sensory and parasympathetic neuropeptides (substance P, calcitonin gene-related peptide and vasoactive intestinal peptide). By contrast, nerve fibers containing neuropeptide Y, a marker of sympathetic neurons, were reduced in number in the diabetic patients. C-fiber function (measured as the axon-reflex-evoked flare response) became impaired with increasing age in all subjects. The diabetic patients, however, showed a reduced flare compared to age-matched healthy controls. The reduction was particularly prominent in the younger patients (20-50 years). There was a greater reduction of the flare in neuropathic patients than in non-neuropathic patients, but there was no correlation between the degree of functional impairment and the duration of the disease.

Interaction between tachykinins and CGRP in human skin

Substance P (SP), neurokinin A (NKA) and calcitonin gene-related peptide (CGRP) coexist in nerve fibres in the skin. CGRP causes erythema upon intracutaneous injection. The erythema is independent of axon reflexes and release of mast cell histamine. SP is known to produce a flare reaction that is dependent on axon reflexes and release of mast cell histamine. The flare reaction to NKA is known to depend predominantly on axon reflexes. The purpose of the present study was to investigate possible cooperation between SP and CGRP. SP was found to shorten the duration of the reddening induced by CGRP, injected concomitantly. NKA did not shorten the duration of the CGRP response. Local elimination of mast cells in the skin by treatment with compound 48/80 had the effect that SP lost its ability to shorten CGRP-evoked erythema. These observations support the suggestion that an SP-evoked release of proteolytic enzymes from mast cells could lead to accelerated degradation of CGRP.

Heterozygous alpha 1-antichymotrypsin deficiency may be associated with cold urticaria

Proteins of the serpin family (serine protease inhibitor) control key steps in the inflammatory, coagulation and complement systems. C1-inhibitor deficiency predisposes to hereditary angioneurotic oedema, and other serpins control proteolytic enzymes that may cause complement activation or the forming of oedema. We investigated whether deficiency of proteins of the serpin family may predispose to cold urticaria and therefore screened 7 male patients with severe cold urticaria for the presence of deficiency alleles of some of the members of the serpin antiprotease family. There were no findings of C1-inhibitor, alpha 1-antitrypsin, alpha 2-antiplasmin, antithrombin III, tissue plasminogen activator inhibitor or thyroxine binding protein deficiency. The prevalence of heterozygous alpha 1-antichymotrypsin deficiency was significantly higher than expected (prevalence ratio 25.8 (95% confidence interval 6.0-112), p < 0.0001). This finding is in concert with previous studies that have shown lower mean levels of alpha 1-antichymotrypsin among patients with cold urticaria and suggests that heterozygous deficiency of this antiprotease, which controls neutrophil cathepsin G and mast cell chymase may predispose to cold urticaria. The present series is, however, small and the results need confirmation in larger materials.

Effects of capsaicin, bradykinin and prostaglandin E2 in the human skin

The actions and interactions of putative mediators of inflammation, such as substance P (SP), histamine, bradykinin and prostaglandins (PGE2) were studied in human skin. In addition, the effects of capsaicin were examined as it is known to release (and to deplete) SP and calcitonin gene-related peptide from C-fibres. The flare evoked by bradykinin was abolished by pretreatment with lignocaine (local anesthetic), compound 48/80 (mast-cell histamine liberator), mepyramine (H1-receptor antagonist) and indomethacin (cyclo-oxygenase inhibitor) but was unaffected by atropine and ketanserin (serotonin antagonist). The weal response was not reduced by any of the drugs. The flare evoked by capsaicin was abolished by lignocaine and indomethacin but was unaffected by compound 48/80, mepyramine, atropine and ketanserin. The weal response was reduced by indomethacin. The flare response to bradykinin seems to reflect the activation of C-fibres and associated mast cells, while the flare response to capsaicin seems to reflect the activation of C-fibres only. Repeated injections of capsaicin and bradykinin produced tachyphylaxis (and cross-tachyphylaxis) and greatly reduced the SP-evoked flare. Capsaicin produced tachyphylaxis also after treatment of the skin with a local anaesthetic, suggesting that it develops independently of C-fibre impulse flow. The tachyphylaxis produced by bradykinin and capsaicin seems to reflect the depletion of messenger peptides from the C-fibres. The flare response to SP following capsaicin- or bradykinin-induced desensitization gradually returned to normal after 5-8 weeks. The erythema evoked by PGE2 was reduced by 30% following pretreatment with lignocaine, mepyramine or compound 48/80.(ABSTRACT TRUNCATED AT 250 WORDS)

Substance P antagonist inhibits immediate and delayed type cutaneous hypersensitivity reactions

The role of substance P (SP) in allergic reactions of the skin was investigated. Spantide, a competitive inhibitor of SP, was injected intracutaneously into the volar aspect of the forearm prior to the following challenges: benzalkonium chloride (irritant delayed reaction), tuberculin (immunological delayed reaction), UVB irradiation, benzoic acid (non-immunological contact urticaria), different food allergens and latex (in patients with immunological contact urticaria). Only the immunological reactions of contact urticaria and the reaction to tuberculin were suppressed by the SP antagonist, indicating that SP is involved in their pathogenesis.

Capsaicin enhances allergic contact dermatitis in the guinea pig

Guinea pigs were sensitized to dinitrochlorobenzene (DNCB) by the intracutaneous route and challenged epicutaneously on the flanks. The intensity of the allergic contact dermatitis was evaluated by inspection and palpation as well as by wet weight determination. With the purpose of diminishing tissue neuropeptides, and substance P in particular, the animals were treated with capsaicin either between induction and challenge, or before sensitization. In comparison with controls, the contact dermatitis was enhanced in both groups of animals treated with capsaicin.

Some neuropeptides as modulators of experimental contact allergy

The rôle of some peptides in allergic contact dermatitis was investigated. The neuropeptides: substance P (SP), vasoactive intestinal peptide (VIP) and somatostatin, as well as the SP antagonist spantide, were injected into the same skin sites as the antigen in patients with contact allergy to nickel. The neuropeptides did not influence the eczematous reaction but spantide diminished it. This might speak for a pathogenetic rôle of SP in allergic contact dermatitis.

Occurrence of substance P, vasoactive intestinal peptide, and calcitonin gene-related peptide in dermographism and cold urticaria

Substance P (SP), calcitonin gene-related peptide (CGRP), and vasoactive intestinal peptide (VIP) were assayed in lesions and normal skin of patients with dermographism and cold urticaria utilizing suction-induced blisters. There was no difference in SP and VIP concentrations between challenged and control skin of urticaria patients. On the whole, however, the concentration of both neuropeptides, and VIP in particular, was higher in the urticaria patients than in control subjects. CGRP levels were not increased. SP and VIP in blood samples from veins draining challenged skin areas were below the detection limit. It is concluded that SP and VIP may potentiate histamine in wheal formation and thus contribute to the increased reactivity of the skin to trauma and temperature changes in patients with physical urticaria.

Effects of substance P, neurokinin A and calcitonin gene-related peptide in human skin and their involvement in sensory nerve-mediated responses

The effects evoked by intradermal injections of substance P (SP), neurokinin A (NKA) or calcitonin gene-related peptide (CGRP) were studied in 51 non-atopic subjects. SP and NKA produced flare and weal, and CGRP produced an indurated erythema. The reactions to SP were strong, the flare being maximal 3-5 min after injection and the weal after 10-15 min. NKA evoked a much weaker flare and a slightly weaker weal than did SP. CGRP produced a prominent long-lasting, indurated erythema with pseudopodia surrounded by a pallor edge. The mode of action of the three peptides was studied by pretreatment of the skin with the histamine-releasing compound 48/80, the H1-antagonist mepyramine or the local anesthetic xylocaine. The results suggest that mast-cell histamine and an intact sensory nerve supply are essential for the flare response to both SP and NKA. The weal response to SP was somewhat reduced by pretreatment with either 48/80 or xylocaine. The weal response to NKA, however, did not seem to depend upon either mast cells or sensory nerve fibres. The erythema evoked by CGRP was not suppressed by pretreatment with xylocaine, compound 48/80 or mepyramine, suggesting a direct action of CGRP on the blood vessels. The interaction between SP and CGRP was studied in subjects receiving a low dose of CGRP and increasing doses of SP or a low dose of SP and increasing doses of CGRP. CGRP did not potentiate the SP-evoked flare and weal and SP did not seem to enhance the response to CGRP.