Debunking the Myth of Wool Allergy: Reviewing the Evidence for Immune and Non-immune Cutaneous Reactions

Clinically uninvolved but not healthy-The skin of patients with atopic dermatitis is primed for itch and inflammation

BACKGROUND

Atopic dermatitis (AD) is a highly prevalent inflammatory skin disorder characterized by episodic exacerbations and remissions. Why the clinically healthy skin of AD patients becomes rapidly inflamed and very pruritic is poorly understood.

OBJECTIVE

To investigate cowhage- and histamine-induced itch and skin expression levels of their target receptors in lesional and non-lesional skin of AD, compared to the skin of patients with psoriasis, chronic spontaneous urticaria (CSU) and healthy subjects.

METHODS

Patients with AD, psoriasis and chronic spontaneous urticaria (CSU) as well as healthy control subjects (HC) (n = 20 each) were assessed for differences in itch parameters, neurogenic flare reaction and local blood flow responses to skin provocations with cowhage and histamine. Skin biopsies from 10 AD, 10 psoriasis,11 CSU and 12 HC were obtained to assess expression of protease-activated receptors 2 and 4 (PAR-2, PAR-4), histamine H1 and H4 receptors (H1R, H4R), and mast cells.

RESULTS

Provocation of non-lesional skin of AD patients with cowhage resulted in prolonged itch (p = 0.020), which was not observed in psoriasis and CSU. Significantly prolonged and more intense cowhage- and histamine-induced itch (for duration, peak and overall intensity) was also observed in lesional AD skin. Diminished neurogenic flare reaction and blood flow after histamine provocation were shown in AD and psoriasis patients. Non-lesional AD skin along with lesional AD and psoriasis skin showed an increased expression of PAR-2 and PAR-4, H1R and H4R. Mast cell number was higher in lesional AD and psoriasis skin (p = 0.006 and p = 0.006, respectively).

CONCLUSION

The non-lesional skin of AD patients markedly differs from healthy skin in cowhage-induced itch responses and the expression of receptors for proteases and histamine. Proactive therapeutic interventions that downregulate these receptors may prevent episodic exacerbation in AD.

Hand eczema and skin complaints in particulate matter-exposed occupations - firefighters, chimney sweepers, and ferrosilicon smelter workers in Norway

BACKGROUND

The objective was to investigate self-reported hand eczema, and skin complaints at other skin locations among workers exposed to particulate matter, especially ultrafine particles.

METHOD

We conducted a cross-sectional study on workers from one ferro-silicon smelter plant, eight chimney sweeper stations and one firefighter station across Norway. Participants answered an extended version of the Nordic Occupational Skin Questionnaire (NOSQ-2022), with additional questions about whole-body skin complaints and visible dust deposition. Results are presented as descriptive data using firefighters as reference group. Odds ratio (OR) was calculated using logistic regression on lifetime prevalence of hand eczema adjusted for potential confounders and mediators. P-values were calculated using likelihood ratio test against the crude OR.

RESULTS

A total of 186 participants answered the questionnaire: 74 chimney sweepers, 52 firefighters and 60 smelter workers. Participation rate was 95.0, 94.5 and 63.6%, respectively. Lifetime prevalence of hand eczema was 9.5, 9.6, and 28.3%, respectively. The point prevalence of hand eczema was 1.4, 1.9 and 10.0%, respectively. We estimated OR for lifetime hand eczema in smelter workers to 4.36 [95% CI: 1.31-14.43, p = 0.016] and for lifetime skin complaints in other locations to 2.25 [95% CI: 0.98-5.18, p = 0.058]. The lifetime prevalence of skin complaints at other locations was 18.9, 23.1 and 40.0%, respectively. The point prevalence was 14.9, 9.6 and 16.7%, respectively. These estimates were not statistically significant but indicates that smelter workers have more skin complaints also at other locations.

CONCLUSION

This study reports a more than four-fold increased risk of hand eczema in smelter workers, and possibly a higher risk of skin complaints in other body locations, compared to the other occupations. Longitudinal studies with larger population are needed to verify the marked increased risk of eczema among smelters and establish causation.

Lanolin

Lanolin is a complex mixture of high molecular weight esters, aliphatic alcohols, sterols, fatty acids, and hydrocarbons that has been widely used for centuries for its emollient properties. The purification of crude lanolin into lanolin wax and the processing of this wax into various derivatives began in 1882 and continue to this day with newer highly purified anhydrous lanolins. Controversy as to lanolin's allergenicity began in the 1920s and remains an issue. The most appropriate patch test preparation(s) for detecting allergy remain disputed. Detection of lanolin-induced contact dermatitis in diseased skin by patch testing on normal skin may lead to false negative results. Patients with a positive patch test to lanolin may tolerate use of lanolin on normal skin. Although lanolin is a weak sensitizer and the frequency of contact allergy to it in the European population reportedly is 0.4%, there are high-risk concomitant conditions: stasis dermatitis, leg ulcers, perianal/genital dermatitis, and atopic dermatitis (AD). Children and the elderly are also at greater risk of developing contact allergy to lanolin, partly because of comorbidities (AD and stasis dermatitis/leg ulcers, respectively). Finally, in the United States, non-Hispanic white patients are more likely than their non-Hispanic black counterparts to be lanolin allergic.

Targeting therapeutic approaches and highlighting the potential role of nanotechnology in atopic dermatitis

Atopic dermatitis is a chronic as well as widespread skin disease which has significant influence on the life attributes of affected people and their families. Systemic immunosuppressive drugs can be utilised for effective care of disease, although they are often prescribed for rigorous disruption or disease that is complicated to manage. Therefore, topical applications of corticosteroids are considered the primary pharmacologic therapies for atopic dermatitis, and research recommends that these medications might be helpful in preventing disease flare-ups. However, topical medicine administration to deeper layers of skin is challenging because of the skin anatomic barrier that restricts deeper drug permeation, and also due to barrier function abnormalities in atopic dermatitis skin, which might result in systemic drug absorption, provoking systemic consequences. Hence, effective management of atopic dermatitis needs new, effective, safe and targeted treatments. Therefore, nanotechnology-based topical therapeutics have attracted much interest nowadays because of their tendency to increase drug diffusion and bioavailability along with enormous drug targeting potential to affected cells, and, thereby, reducing the adverse effects of medications. In this review, we mention different symptoms of atopic dermatitis, and provide an overview of the different triggering factors causing atopic dermatitis, with emphasis on its epidemiology, pathophysiology, clinical features and diagnostic, and preventive measures. This review discusses existing therapeutics for treating atopic dermatitis, and the newer approaches as well as the current classical pharmacotherapy of atopic dermatitis against new nanoparticle skin delivery systems. This review has also briefly summarised the recent patents and clinical status of therapeutic modalities for atopic dermatitis.

A spinal neural circuitry for converting touch to itch sensation

Touch and itch sensations are crucial for evoking defensive and emotional responses, and light tactile touch may induce unpleasant itch sensations (mechanical itch or alloknesis). The neural substrate for touch-to-itch conversion in the spinal cord remains elusive. We report that spinal interneurons expressing Tachykinin 2-Cre (Tac2^Cre) receive direct Aβ low threshold mechanoreceptor (LTMR) input and form monosynaptic connections with GRPR neurons. Ablation or inhibition markedly reduces mechanical but not acute chemical itch nor noxious touch information. Chemogenetic inhibition of Tac2^Cre neurons also displays pronounced deficit in chronic dry skin itch, a type of chemical itch in mice. Consistently, ablation of gastrin-releasing peptide receptor (GRPR) neurons, which are essential for transmitting chemical itch, also abolishes mechanical itch. Together, these results suggest that innocuous touch and chemical itch information converge on GRPR neurons and thus map an exquisite spinal circuitry hard-wired for converting innocuous touch to irritating itch.

Fabric Selection in Atopic Dermatitis: An Evidence-Based Review

BACKGROUND

Clothing fabrics interact closely with the skin to shape our cutaneous microenvironment. Cotton and silk have been traditionally recommended for patients with atopic dermatitis because of reported patient comfort. New synthetic fabrics combine anti-microbial, anti-inflammatory, moisture-wicking, and soothing properties that may augment conventional management strategies in atopic patients.

OBJECTIVE

We review existing and emerging evidence for fabric selection in patients with atopic dermatitis including cotton, wool, lyocell, silk, anionic, cellulosic/cellulose based, zinc oxide coated, citric acid coated, chitosan coated, silver coated, borage seed oil coated, ethylene vinyl, and polyurethane and offer practical suggestions for clothing and bedding choices.

METHODS

A systematic search was conducted on PubMed and EMBASE electronic databases for articles from 1 January, 1994 to 1 January, 2020. Studies were included based on the following inclusion criteria: clinical trial, published in English, and fabric as the main agent being evaluated. Case reports, case series, conference abstracts, reviews, animal studies, and duplicates were excluded. Studies were then manually screened by title, abstract, and full-text articles and selected to specifically describe the effects of fabrics in patients with atopic dermatitis. Both adult and pediatric patient studies were included.

RESULTS

There appears to be an advantage to modern fabric manufacturing and processing techniques that have created smaller diameter, smoother fibers such as super- and ultrafine merino wool and anti-microbial finishes. Traditional cotton and silk fabrics have mixed evidence in improving atopic dermatitis symptoms and severity but have shown to be generally safe. Large-diameter wool has been shown to induce itching and irritation; ultra- or superfine merino wool is non-pruritic and may be recommended as an alternative. Emerging fabrics with potential efficacy in reducing atopic dermatitis severity and Staphylococcus aureus burden include silver-coated, chitosan-coated, and cellulose-based fabrics. Zinc oxide-coated, acid-coated, polyurethane-coated, borage seed oil-coated, anionic, lyocell, and ethylene vinyl fabrics have sparse evidence and require further study before conclusions can be made.

CONCLUSIONS

Appropriate fabric selection can reduce the symptom severity and exacerbations of atopic dermatitis.

Effects of Merino Wool on Atopic Dermatitis Using Clinical, Quality of Life, and Physiological Outcome Measures

Background

Wool clothing may be perceived as a poor choice for use by individuals with sensitive skin or atopic dermatitis.

Objectives

The aims of the study were to evaluate the effect on atopic dermatitis of wearing fine Merino wool clothing versus standard clothing and to assess the effect of Merino wool clothing on quality of life in children and adults with atopic dermatitis 5 years and older.

Methods

Subjects with mild to moderate atopic dermatitis were assessed in a crossover fashion after wearing Merino wool clothing for 6 weeks and standard clothing for 6 weeks, for Eczema Area and Severity Index, Dermatology Life Quality Index, static Investigator's Global Assessment, and skin hydration.

Results

While wearing Merino wool clothing, compared with standard clothing, statistically significant improvements were seen in mean Eczema Area and Severity Index scores, Dermatology Life Quality Index scores, and static Investigator's Global Assessment scores. No significant difference was seen with skin hydration. Wearing Merino wool clothing did not produce any negative cutaneous effects compared with wearing standard clothing.

Conclusions

Merino wool clothing compared with standard clothing provided improvements in severity of atopic dermatitis as well as quality of life in atopic patients.

Bio-Functional Textiles: Combining Pharmaceutical Nanocarriers with Fibrous Materials for Innovative Dermatological Therapies

In the field of pharmaceutical technology, significant attention has been paid on exploiting skin as a drug administration route. Considering the structural and chemical complexity of the skin barrier, many research works focused on developing an innovative way to enhance skin drug permeation. In this context, a new class of materials called bio-functional textiles has been developed. Such materials consist of the combination of advanced pharmaceutical carriers with textile materials. Therefore, they own the possibility of providing a wearable platform for continuous and controlled drug release. Notwithstanding the great potential of these materials, their large-scale application still faces some challenges. The present review provides a state-of-the-art perspective on the bio-functional textile technology analyzing the several issues involved. Firstly, the skin physiology, together with the dermatological delivery strategy, is keenly described in order to provide an overview of the problems tackled by bio-functional textiles technology. Secondly, an overview of the main dermatological nanocarriers is provided; thereafter the application of these nanomaterial to textiles is presented. Finally, the bio-functional textile technology is framed in the context of the different dermatological administration strategies; a comparative analysis that also considers how pharmaceutical regulation is conducted.