Contact dermatitis in older adults: a review of the literature

Patch Test Results Among Older Adults: A Retrospective Analysis of the North American Contact Dermatitis® Group Data (2009-2020)

Background: Allergic contact Dermatitis® (ACD) in older adults (OA) represents a significant health burden, but few studies examine the prevalence and characteristics of contact allergy and ACD in this population. Objective: To compare positive and clinically relevant patch test results in OA versus younger adults (YA) and children. Methods: Retrospective analysis of patch test results obtained in OA (≥65 years), YA (19-64 years), and children (≤18 years) by the North American Contact Dermatitis® Group, 2009 to 2020. Results: Of 28,177 patients patch tested, 5366 (19.0%) were OA. OA were more likely to have a final primary diagnosis of ACD as compared with YA (50.8% vs 49.2%, P = 0.035) and children (44.6%, P < 0.0001). The primary site of Dermatitis® also differed by age group, with OA having a higher proportion of Dermatitis® affecting the trunk, scalp, anogenital region, and "under clothing," and a lower proportion of Dermatitis® affecting the face, lips, and feet. Limitations: Retrospective design, lack of follow-up, and referral population. Conclusion: OA were as likely and were statistically even more likely to have a final primary diagnosis of ACD compared with YA and children. Anatomic site of Dermatitis® also differed by age group. This underscores the need for patch testing in OA when ACD is suspected.

Diagnosis and Management of Common Inflammatory Skin Diseases in Older Adults

Inflammatory skin conditions affect people of all ages, genders, and races. These common conditions are frequent causes of visits to the dermatologist. The geriatric population is often afflicted by these conditions because many are chronic and relapsing diseases. These inflammatory conditions include but are not limited to psoriasis, atopic dermatitis, contact dermatitis, seborrheic dermatitis, rosacea, and Grover disease. Chronic inflammatory skin conditions place a large burden on the health care system in the United States and have many associated comorbidities. This article discusses these inflammatory dermatoses that affect the geriatric population and common therapeutic options.

Achalasia is Strongly Associated With Eosinophilic Esophagitis and Other Allergic Disorders

BACKGROUND & AIMS

Achalasia has been assumed to be an autoimmune disease targeting esophageal myenteric neurons. Recently, we proposed an alternative hypothesis that achalasia sometimes might be allergy-driven, caused by a form of eosinophilic esophagitis (EoE) in which activated eosinophils and/or mast cells infiltrating esophageal muscle release products that disrupt motility and damage myenteric neurons. To seek epidemiologic support for this hypothesis, we identified patients with achalasia in the Utah Population Database, and explored their frequency of having EoE and other allergic disorders.

METHODS

We used International Classification of Diseases codes to identify patients with achalasia and allergic disorders including EoE, asthma, atopic dermatitis, contact dermatitis, allergic rhinitis, allergic conjunctivitis, hives/urticaria, and anaphylaxis. We calculated relative risk (RR) for each allergic disorder by comparing the number observed in patients with achalasia with the expected number in individuals matched for birthyear and sex, and we performed subanalyses for patients age ≤40 versus age >40 years.

RESULTS

Among 844 patients with achalasia identified (55% female; median age at diagnosis, 58 years), 402 (47.6%) had ≥1 allergic disorder. Fifty-five patients with achalasia (6.5%) had EoE (1.67 EoE cases expected), for a RR of 32.9 (95% confidence interval, 24.8-42.8; P < .001). In 208 patients with achalasia age ≤40 years, the RR for EoE was 69.6 (95% confidence interval, 46.6-100.0; P < .001). RR also was increased significantly for all other allergic disorders evaluated (all greater than 3-fold higher than population rates).

CONCLUSIONS

Achalasia is strongly associated with EoE and other allergic disorders. These data support the hypothesis that achalasia sometimes might have an allergic etiology.

Allergic Contact Dermatitis in the Older Adults: A Comparative Cross-Sectional Study

Background: Allergic contact dermatitis (ACD) is a significant health problem in older adults. Reports in the literature regarding the prevalence of ACD in older adults are various and inconsistent. In contrast, the data regarding contact irritant dermatitis are more consistent. Objective: To compare ACD characteristics in older adults versus the adult population aged 18-45 years. Methods: We conducted a retrospective controlled study. Data were obtained from the medical records of 4199 patients. We collected information regarding age, gender, atopic diathesis, anatomical distribution of the rash, reactions to patch tests, and final diagnosis. Results: The frequency of positive reactions in patch testing was lower in the older adult group than in the younger population, but the frequency of clinically relevant positive reactions was higher in the older adults. There was no statistically significant difference in the final diagnosis of ACD between the groups. The most common allergens among the older adult population were fragrance mix, preservatives (Methylchloroisothiazolinone/methylisothiazolinone [MCI/MI]), and nickel sulfate. Conclusion: This study, the first of its kind in Israel to include a large group of older adult patients, contributes to a better understanding of clinical parameters related to ACD among older adults. Consequently, it will hopefully contribute to lowering the disease burden.

Contact Allergy in the Elderly: A Study of 600 Patients

The proportion of elderly in the general population is increasing. Ageing of the skin and immune system can modify the features of contact hypersensitivity (CH). The number of epidemiological studies according to the age-related features of CH is very limited. We aimed to analyse the clinical characteristics of CH in an elderly patient population. A total of 600 patients (patient age > 60 years old) were patch tested with the European Environmental Baseline Series (EEBS) and 440 of them with the Complementary Fragrance Series (CFS) at the same time according to the actual international methodological standards in the Allergy Outpatient Unit of Department of Dermatology, Venereology and Dermato-Oncology of Semmelweis University between 2015−2019. Out of 600 tested patients, 54.8% had at least one allergen positivity. Female predominance was observed (78.7%). The most common diagnosis was contact dermatitis (63.7%), followed by psoriasis (6.2%). Most of the cases (58.0%) were found in the age group of 60−69. The five most common contact allergens were benzoic acid, methylisothiazolinone (MI), wood tar, nickel, and balsam of Peru. Allergic skin symptoms are present in all ages and also in the elderly. According to our data, the most common contact allergens are preservatives, followed by balsam of Peru among men and nickel among women. In case of contact dermatitis, stasis dermatitis, rosacea, and atopic dermatitis are worth patch testing to verify CH even in those above 60 years old.

The benefit of late readings in patch testing depends both on allergen and patient characteristics

BACKGROUND

Patch test (PT) readings are recommended after 48 h and 72 h (D3). An additional day 7 (D7) reading has been suggested by some, although data on efficient patient selection are scarce. We investigated positive D7 reactions regarding (i) allergens in the baseline series and additional PT series of the German Contact Dermatitis Research Group (DKG) and (ii) characteristics of the patients tested.

METHODS

Retrospective, multicentre analysis of 190 allergens derived from 17 DKG test series in 4687 patients with an additional D7 reading. Patients were patch tested with the baseline series and additional series, if required. Occurrence of novel D7 reactions as well as increasing skin reactions from D3 to D7 was analysed separately.

RESULTS

Depending on the allergen tested, waiving D7 readings would have missed 4.4-26.8% of positive PT results. Patch test series with the highest number of novel D7 reactions were baseline series, metal series, and leather/shoe series. New positive reactions on D7 were associated with age over 50 years and with a negative irritant control containing sodium lauryl sulphate. Of note, application of the PT allergens for 48 h instead of 24 h was positively associated with late PT reactions.

CONCLUSION

Within the most frequently tested allergens, without late readings, on average 11.7% of sensitizations would have been missed. Novel late reacting allergens were identified. This study comprehensively dissects patient-, allergen- and test-dependent parameters in support for D7 readings. We propose to always consider late readings individually based on effort-benefit considerations.

Prevalence and trend of allergen sensitization in patients with a diagnosis of stasis dermatitis referred for patch testing, North American contact dermatitis group data, 2001-2016

BACKGROUND

Few studies explored the relationship between stasis dermatitis (SD) and allergic contact dermatitis (ACD).

OBJECTIVE

To examine trends, associations, and clinical relevance of ACD in patients referred for patch testing who had a final SD diagnosis.

METHODS

Retrospective analysis from 2001 to 2016 of 38,723 patients from the North American Contact Dermatitis Group.

RESULTS

After patch testing, 303 (0.7%) patients were diagnosed with SD; 46.7% had a concomitant diagnosis of ACD. Patients with vs. without a final SD diagnosis had similar proportions of ≥ 1 positive allergic reaction (59.7% vs. 64.7%; Chi-square, P = 0.0724) but higher odds of allergic reactions to fragrance mix I, bacitracin, quaternium-15, Myroxylon pereirae, benzalkonium chloride, ethyleneurea melamine formaldehyde, diazolidinyl urea, and propylene glycol. The most commonly relevant allergens in patients with final SD diagnosis were fragrance mix I, Myroxylon pereirae, bacitracin, quaternium-15, and formaldehyde. The most common allergen sources were personal care products, topical medications and other health aid products.

CONCLUSION

Nearly half of patients with a final SD diagnosis were also diagnosed with ACD, supporting the role of patch testing in select SD patients.

Patch Test Reactions Associated With Topical Medications: A Retrospective Analysis of the North American Contact Dermatitis Group Data (2001-2018)

BACKGROUND/OBJECTIVES

Topical medications may lead to allergic contact dermatitis. This study characterized positive patch test reactions associated with medications in patients evaluated by the North American Contact Dermatitis Group (NACDG).

METHODS

This study is a retrospective analysis of the NACDG data (2001-2018). Patients with at least 1 positive patch test reaction associated with a medication source were included. Allergens, reaction characteristics, clinical relevance, and source details were tabulated.

RESULTS

Of 43,722 patients, 6374 (14.6%) had positive allergic patch test reactions associated with 1 or more topical medication sources. Patients with versus without allergic reactions to medications were more likely to be older than 40 years (P < 0.0001) and/or have primary sites of dermatitis on the legs, anal/genital region, or trunk (P < 0.0001). There were 8787 reactions to NACDG allergens; the most common were neomycin (29.4%), bacitracin (29.1%), propylene glycol 100% (10.6%), tixocortol-17-pivalate (10.0%), lidocaine (7.9%), budesonide (4.9%), and dibucaine (4.4%). Propylene glycol 100% was the most common inactive ingredient (10.6%). Current relevance was present in 61.0%. A total of 6.5% of the individuals with medication allergy would have had 1 or more positive patch test reactions missed if only tested to the NACDG screening series.

CONCLUSIONS

Positive patch test reactions associated with topical medications were common (14.6%), and most were clinically relevant. Patients with topical medication allergy were twice as likely to have anal/genital involvement. Active ingredients, especially neomycin, bacitracin, and tixocortol-17-pivalate, were frequent culprits.

Nickel Hypersensitivity to Atrial Septal Occluders: Smoke Without Fire?

Nickel is one of the most common contact allergens worldwide; it is used as the main component of the devices used for atrial septal defects (ASDs) and patent foramen ovale (PFO) closure. Developing nickel hypersensitivity after PFO/ASD occlusion is significantly rarer described in medical literature than typical nickel contact sensitization. The exact pathophysiological mechanism of this "device syndrome" remains unknown, and many question the real incidence or even the existence of this clinical entity. Nevertheless, it has been associated with a wide spectrum of symptoms, including chest pain, migraines, palpitation, and dyspnea. Skin patch tests are the first-line approach to diagnose nickel hypersensitivity. However, diagnostic criteria for the device syndrome have not been developed, and diagnosis in reported cases is established by a process of elimination. Management-drug therapy (corticosteroids, clopidogrel, etc.) or even surgical explantation in severe cases-of patients developing such clinical manifestations after percutaneous PFO/ASD occlusion is empirical. Undoubtedly, endocardiac device-related nickel hypersensitivity requires more focused research to discover the underlying mechanism as well as to develop reliable prognostic tests for detecting high-risk patients and preventing severe nickel hypersensitivity reactions.

Postoperative contact dermatitis caused by skin adhesives used in orthopedic surgery: Incidence, characteristics, and difference from surgical site infection

Skin adhesives are used to close clean surgical wounds. We aimed to investigate the incidence of skin adhesive-related contact dermatitis and the characteristics that differentiate it from a surgical site infection.We retrospectively analyzed patients whose surgical wound was closed using a liquid skin adhesive (Dermabond Prineo skin closure system, Ethicon, NJ) by a single surgeon between March 2018 and June 2020. Medical records were reviewed to evaluate complications indicating contact dermatitis, including wound infections and hematomas.We included 143 patients (men, 59; women, 84; mean age, 60.8 years). No patient had an early surgical site infection or wound dehiscence, but 4 (2.8%) developed postoperative contact dermatitis (week 7, 1; week 4, 2; day 9, 1). Manifestations included eczema and pruritus, without local heat or wound discharge. All cases resolved without complications, including infection.Contact dermatitis occurred in 2.8% of patients who received liquid skin adhesive, and the symptoms differed from those of surgical site infection. Patients should be informed about the risk of contact dermatitis before applying a liquid skin adhesive.

Potential Co-Factors of an Intraoral Contact Allergy-A Cross-Sectional Study

The aim of this cross-sectional study was to evaluate the frequency of dental allergens and potential co-factors, especially hypothyroidism, for patients with an intraoral contact allergy. From 2015 to 2016, patients with confirmed symptoms of an intraoral contact allergy (study group SG n = 50) were recruited in the dental clinic of the University of Leipzig. The participants of the control group (CG n = 103) were patients without oral diseases or intraoral symptoms of a contact allergy. For the data collection, a new "Allergy questionnaire" was developed. Information on allergies and general diseases were collected. The statistical analysis was carried out with SPSS 23.0. Sensitizations/allergies to metals and composites were higher in SG compared to CG. Of all study participants (n = 148), 14.2% (n = 21) had a nickel allergy. In 18% (n = 8) of the SG a cobalt allergy based on all metal allergens could be seen. In addition, an association between a nickel and cobalt allergy was found. Hypothyroidism occurred significantly more frequently (p = 0.049) in SG than in CG. Sensitizations and allergies can occur to metals in dental alloys. Hypothyroidism increased the risk of having an allergy threefold.

Aging-associated alterations in epidermal function and their clinical significance

Chronologically-aged skin displays multiple functional changes in both the dermis and the epidermis. It appears that epidermal dysfunction, compromised permeability homeostasis, reduced stratum corneum hydration and elevated skin surface pH predispose to the development of aging-associated cutaneous and extracutaneous disorders. Improvements in epidermal function have been shown to be an effective alternative therapy in the prevention and treatment of some aging-associated cutaneous disorders, including eczematous dermatitis, pruritus, and xerosis. Recent studies demonstrated that epidermal dysfunction leads to the development of chronic, low-grade systemic inflammation, termed ‘inflammaging,’ which is linked to the development of aging-associated systemic disorders. Thus, correction of epidermal dysfunction could comprise a novel strategy in the prevention and treatment of aging-associated systemic disorders as well. In this review, we summarize aging-associated alterations in epidermal function, their underlying mechanisms, and their clinical significance. Regimens to improve epidermal function in the elderly are also discussed.

Efficacy and Safety of Alitretinoin Therapy in Korean Elderly Patients with Chronic Hand Eczema: A Retrospective Single Center Study

Background

Chronic hand eczema (CHE) tends to be refractory to conventional therapy. Previous clinical trials have found that alitretinoin is an effective and well-tolerated treatment for CHE. However, there is a relative lack of data on the effectiveness of alitretinoin in elderly patients.

Objective

The aim of this study was to investigate the efficacy and safety of oral alitretinoin in elderly patients with moderate to severe CHE in Korea.

Methods

We retrospectively investigated 46 CHE patients who were treated with either 10 mg or 30 mg of alitretinoin between June of 2016 and July of 2018. The physician's global assessment (PGA) was used to evaluate treatment efficacy. All adverse events were retrospectively evaluated with respect to laboratory testing, including complete blood cell count, fasting blood chemistry, lipid profile, and liver and thyroid function tests.

Results

The mean patient age in this study was 71.0±5.1 years. The treatment period was over eight weeks. A total of 38 of 46 patients (82.6%) exhibited clinical improvement with PGA ratings of ‘clear’ or ‘almost clear.’ There were 13 patients (28.3%) who experienced an adverse effect, with the most common being headache (13.0%) and gastrointestinal symptoms (8.7%) followed by xerosis (6.5%). A total of 13 patients developed or exhibited worsening hypertriglyceridemia (28.3%).

Conclusion

Alitretinoin can be considered a safe and effective treatment option in elderly patients with moderate to severe CHE.

Dermatology ECHO: A case presentation demonstrating benefits of specialty telementoring in primary care

Allergic contact dermatitis (ACD) is a common dermatologic disorder that is estimated to affect 15-20% of the general population. Because of its prevalence, it may be expected that ACD should be easily recognized. However, it can present with many clinical variations that may complicate diagnosis. Although ACD is a treatable condition, patients from rural and underserved areas suffer if timely access to specialty care is limited. Dermatology Extension for Community Healthcare Outcomes (Dermatology ECHO) telemedicine sessions were created to mentor rural primary care providers (PCPs). To illustrate their benefit, we present the case of a 19-year-old female patient who suffered from worsening undiagnosed ACD for over nine months following a laparoscopic appendectomy. During that time, the surgeon and multiple PCPs treated her with antibiotics, antivirals, and Scabicide without improvement in her condition. The de-identified patient case was presented by her PCP during the Dermatology ECHO session. The Dermatology ECHO specialty team mentored and educated the PCP in the diagnosis and treatment of ACD. After making the diagnosis, the patient received new treatment and her condition improved significantly. Dermatology ECHO provides a knowledge-sharing network for participating PCPs that may improve patient outcomes and reduce patient suffering.

Causes, pathophysiology, and treatment of pruritus in the mature patient

Chronic itch is a common and debilitating health condition in the elderly. There are several common causes of itch in the mature population, such as skin xerosis, immunosenescence, and neuropathic changes. In addition, skin diseases, such as seborrheic dermatitis and stasis dermatitis, systemic conditions (end-stage renal disease and diabetes), or psychogenic derailments, such as depression, anxiety, and dementia, can all serve as triggers of pruritus. Polypharmacy, a common occurrence among the elderly population, may also serve as a cause of itch that may or may not be accompanied by dermatitis. Such medications as μ opioids and calcium channel blockers have been found to have a connection with pruritus in the advanced aging population. Determining the exact trigger for pruritus in the elderly may be especially challenging, because itch can be idiopathic in many cases. The role of treatments should not only take into account elimination of various underlying cutaneous, systemic, or psychogenic conditions associated with itch but also focus on the skin changes that are characteristic of the aging process. Development of such treatment options can be guided by elucidation of the mechanisms underlying the pathophysiology of itch in the geriatric population.

Chronic pruritus in the elderly: pathophysiology, diagnosis and management

Chronic itch in the elderly is a common problem, with a significant impact on quality of life and sleep in elderly patients. Chronic itch may be attributable to several causes, including dry skin, immunosenescence and neural degeneration. Itch may also be caused by skin diseases, such as seborrhoeic dermatitis and stasis dermatitis; systemic conditions, such as end-stage renal disease and diabetes; and psychogenic conditions, such as depression and anxiety. The use of polypharmacy may also cause itch, with or without a rash. Specifically, thiazides and calcium channel blockers have been known to cause itch in elderly patients. Management should be tailored according to the underlying dermatological or systemic aetiology of itch. Topical treatment is the mainstay of therapy, providing special emphasis on skin hydration and barrier repair. In addition, topical and oral medications that target the nervous system and reduce neuronal hypersensitization, such as gabapentin and selective antidepressants, have a role in treating patients with severe chronic itch. Furthermore, management must account for changes in metabolism and pharmacokinetics of drugs in the aging population in order to prevent the occurrence of adverse effects.

Changes in dermal matrix in the absence of Rac1 in keratinocytes

Keratinocytes, in response to irritants, secrete pro-inflammatory mediators which recruit and activate immune and mesenchymal cells, including fibroblasts, to repair the skin. Fibroblasts respond by synthesising collagen and promoting the crosslinking extracellular matrix (ECM). We recently showed that the deletion of Rac1 in keratinocytes causes heightened inflammation due to aberrant crosstalk with immune cells. Indeed, the skin of these mice shows a higher inflammatory response to the induction of irritant contact dermatitis (ICD), and also even to treatment with a vehicle alone, compared with controls. As inflammation is intimately linked with fibrotic disease in the skin, this raised the question as to whether this deletion may also affect the deposition and arrangement of the dermal ECM. This study assessed the effects of Rac1 deletion in keratinocytes and of the heightened inflammatory status by induction of ICD on the tissue localisation and arrangements of dermal collagen. Qualitative analysis did not reveal evidence for the formation of pathologies in the dermis. However, quantitative analysis did reveal some perturbations in the dermal matrix, namely that only the combination of the lack of Rac1 and ICD affects the architectural organisation of the dermal collagen, and that a higher inflammatory state in the tissue (i.e. when Rac1 is deleted in the keratinocytes or ICD is induced in the skin, or a combination of both) influences the diameter of the collagen fibrils. It is proposed that this increase in the diameter of collagen fibrils due to inflammation may serve as pre-fibrotic marker enabling earlier determination of fibrosis and earlier treatment. This study has revealed previously unknown effects on the ECM due to the deletion of Rac1 in keratinocytes.

Elderly adults and skin disorders: common problems for nondermatologists

Diseases of elderly adults are becoming increasingly important as life expectancy gradually rises worldwide. To promote healthy aging, it is important to understand the skin changes associated with aging. This review focuses on the special considerations for some of the more common dermatological disorders in elderly adults and examines presentation, contributing factors, and association with systemic diseases.

Pruritus in elderly patients--eruptions of senescence

Geriatric patients are frequently afflicted by pruritic dermatoses. Most pruritic elderly patients present with a skin eruption. The high prevalence of pruritic inflammatory skin disorders in elderly patients is a consequence of three physiological changes that occur with aging: (1) the epidermal barrier repair is diminished; (2) the immune systems of elderly patients are activated and have defective Th1 function along with enhanced Th2 function (immunosenescense); and (3) neurodegenerative disorders may lead to pruritus by their central or peripheral effects. These consequences of aging may all afflict the same patient, explaining why elderly people often have multiple overlapping skin conditions. The following article outlines the pathogenesis of the most common forms of pruritic skin disease in elderly patients and the hallmarks that allow the dermatologist to establish an accurate diagnosis and also suggests a management strategy for each common type of pruritic skin disease in the elderly patient.

A 3-in-1 perineal care washcloth impregnated with dimethicone 3% versus water and pH neutral soap to prevent and treat incontinence-associated dermatitis: a randomized, controlled clinical trial

PURPOSE

We compared the effectiveness of a 3-in-1 perineal care washcloth versus standard of care (water and pH neutral soap) to prevent and treat incontinence-associated dermatitis (IAD). The product under study was a soft, premoistened washcloth, including a 3% dimethicone formula, with cleansing, moisturizing, and barrier protection properties.

DESIGN

Randomized, controlled clinical trial.

SUBJECTS AND SETTING

The study sample comprised a random sample of 11 nursing home wards (6 experimental and 5 control) in a convenience sample of 4 nursing homes in Belgium. The sample included nursing home residents at risk for and/or affected by IAD defined as incontinent of urine, feces, urine/feces, and/or having erythema of the perineal skin (not caused by pressure/shear), and/or having an edematous skin in the genital area.

METHODS

Participants in the experimental group were treated according to a standardized protocol, including the use of a 3-in-1 perineal care washcloth impregnated with a 3% dimethicone skin protectant. Participants in the control group received perineal skin care with water and pH neutral soap, the standard of care in Belgian nursing homes. The study period was 120 days. Data were collected between February and May 2010. Incontinence-associated dermatitis prevalence and severity were assessed using the IAD Skin Condition Assessment Tool. The surface (cm), redness, and depth of the perineal lesion were assessed daily by the nurses. This tool generates a cumulative severity score (maximum score = 10) based on area of skin affected, degree of redness, and depth of erosion.

RESULTS

Four hundred sixty-four nursing home residents were assessed and 32.9% (n = 141) met the criteria for inclusion, including 73 subjects in the experimental group and 68 in the control group. Baseline IAD prevalence was comparable in both groups (experimental: 22.3% vs control: 22.8%, P = .76). Baseline IAD severity was 6.9/10 in the experimental group and 7.3/10 in the control group. A significant intervention effect on IAD prevalence was found (experimental: 8.1% vs control: 27.1%, F = 3.1, P = .003). A nonsignificant effect on IAD severity could be determined (experimental: 3.8/10 vs control: 6.9/10, F = 0.8, P = .06).

CONCLUSION

The use of a 3-in-1 washcloth, impregnated with a 3% dimethicone formula, resulted in a significantly reduced prevalence of IAD and a trend toward less severe lesions. These findings provide indicative evidence for the use of 3-in-1 perineal care washcloth as an effective intervention against the use of water and a pH neutral soap to prevent and/or treat IAD.

[Indications for referral to a skin allergy unit]

Contact dermatitis is one of the most common reasons for consultation in dermatology. However, general dermatologists do not always appreciate the importance of patch testing. These tests should ideally be performed in specialist skin allergy units, most importantly in cases suggestive of contact dermatitis, severe acute dermatitis, chronic persistent dermatitis, and dermatitis affecting the eyelids, genital region or adjacent to venous ulcers. Eczematous changes in pre-existing skin lesions or lesions at atypical sites in patients diagnosed with atopic eczema should also be investigated. Finally, cases diagnosed as occupational dermatitis can be best managed by the workers' health insurance scheme.