CD13 Remote review for final patch test reading: a virtual reality?

Abstract

Patch test reading at day 7 is suggested in current national (British Association of Dermatologists 2017) and international (European Society of Contact Dermatitis 2015) guidelines to identify late positive reactions. Allergens most established with late reactions are metals, antibiotics, acrylates and preservatives (Viggiano T, Yiannias JA, Yang YW. A retrospective review of late delayed positive patch testing greater than day 8 at Mayo Clinic from 2001 to 2020. Dermatitis 2022; 33:411–16). We report a case of significantly delayed contact dermatitis to four acrylates and ethyl paraben in a 49-year-old immunocompetent woman. She was referred to the cutaneous allergy clinic for patch testing following a rash affecting the torso after application of a sunscreen during a sunny holiday. She reported historical skin irritation after the use of nail lacquer and at the site of a caesarean section wound that was closed with skin glue 14 years prior. Patch test reading at day 4 (96 h) was negative; positive reactions to ethyl paraben, 2-hydroxyethylmethacrylate and ethyl cyanoacrylate appeared at day 23 (552 h). Positive reactions to hexanediol diacrylate and triethylene glycol diacrylate appeared at day 31 (744 h). These were communicated to us by the patient via email, with photographs clearly showing the development of new positive reactions. Of note, there was no reaction to the sunscreen product, although ethyl paraben was identified in the ingredients list, as well as two acrylate-containing polymers. Sensitization from diagnostic patch testing carried out to accepted international guidelines is rare but can occur with some allergens such as strong sensitizers, including paraphenylenediamine. The allergens identified in our case are found commonly in everyday cosmetics, adhesives and preservatives, including some that the patient had identified previous exposure to. Acrylates are acknowledged for causing potential delayed positive reaction by day 8 (Viggiano et al.); one case report describes true allergic acrylate reaction in a dental worker after 5 weeks (Fowler JF Jr. Late patch test reaction to acrylates in a dental worker. Am J Contact Dermat 1999; 10:224–5). There are no established reports of late positive reactions to ethyl paraben. With increasing online resources, delayed reactions beyond day 7 can be established with patient-initiated remote review of photographs taken during and subsequent to patch testing appointments. This case highlights the importance of keeping channels open for patients to contact the cutaneous allergy team after the final in-person reading to ensure (very) late allergen reactions are not missed.