Patch Test Clinic Start-up: From Basics to Pearls

Various techniques for marking patch test sites

Patch test helps in identifying the allergen causing allergic contact dermatitis. Proper identification of the site of individual patch test allergen is very important for identifying the positive allergen. In this article, various techniques for markings patch test sites are discussed.

Methotrexate and Patch Testing: A Retrospective Review

BACKGROUND

Patch testing while taking systemic immunosuppressants is sometimes unavoidable. Methotrexate (MTX) is the immunosuppressant currently considered least likely to negatively impact patch testing.

OBJECTIVE

The aim of the study was to characterize a cohort of patients patch tested while taking MTX.

METHODS

This is a retrospective review of patients patch tested at the University of North Carolina Dermatology in Chapel Hill, North Carolina, from 2010 to 2019, comparing patch test results of patients taking MTX with those of a control group.

RESULTS

An overall 52.8% positivity rate (356/674) was observed. Sixty two of 674 patients were patch tested while taking MTX, with a 46.8% positivity rate (29/62) compared with 53.4% (327/612) in the control group. The control group experienced 975 reactions, including 637 1+ reactions, 291 2+ reactions, and 47 3+ reactions. The MTX group experienced 50 reactions, including thirty-two 1+ reactions, fourteen 2+ reactions, and four 3+ reactions. The difference between the distributions was not statistically significant. Mean weekly MTX dose was 15.6 mg, whereas mean total accumulated dose was 251.6 mg. There was no statistically significant difference between weekly dose and total accumulated dose in patients with positive or negative results.

CONCLUSIONS

In our cohort, MTX had no discernible effect on patch test results, supporting use during patch testing with minimal false-negative risk.

Contact dermatitis: An important consideration in leg ulcers

The prevalence of chronic wounds is increasing with the aging population, with 1% to 2% of the worldwide population experiencing leg ulcers and positive patch tests reported in up to 75% of this population. With the introduction of modern dressings and compression therapies, clinicians should be cognizant of the potential risk of contact dermatitis in patients with leg ulcers. Contact dermatitis (both allergic and irritant) to wound products may present as maceration, pain, and overall impaired wound healing. Herein, we review the literature on contact dermatitis to wound-care products.