CD10 Challenges with chambers: a case of contact allergy to patch test units

Abstract A 26-year-old healthy female biomedical scientist presented with four episodes of facial dermatitis over a 2-year period. The rash was characterized by erythema and swelling of the cheeks, chin and forehead, with each episode lasting about a week. Patch testing was initially conducted to the British Society for Cutaneous Allergy (BSCA) standard, cosmetics, fragrances, hairdresser and bakery series using IQ UltraTM patch test units. However, due to a strong positive reaction to the adhesive foam portion of the IQ UltraTM patch test units, accurate readings were not possible. Consequently, testing was repeated using Finn chambers. Additional patch testing with empty IQ Ultra™ patch test units again resulted in positive reactions on day 2 and day 4, confirming the patient’s sensitivity to the foam. As a result, Finn chambers were used for repeat patch testing. Series applied with Finn chambers included the standard and cosmetics series with additional application of the acrylate, epoxy and paraben series. Positive reactions were noted to balsam of Peru, epoxy resin (bisphenol A), 2-n-octyl-4-isothiazolin-3-one, tert-butylhydroquinone, oleamidopropyl dimethylamine, caine mix III and para-phenylenediamine (PPD). The reactions were of current relevance, and guidance on avoiding identified allergens, and relevant information leaflets were provided. The Chemotechnique IQ UltraTM patch test unit information leaflet suggested that the unit was composed of nonwoven carrier tape and absorbent cellulose central filter paper, surrounded by polyurethane foam coated with medical-grade acrylic [Chemotechnique Diagnostics. Patch testing. Available at: https://www.chemotechnique.se/patch-testing (last accessed 13 March 2025)]. The exact composition of the acrylates used in the test chambers is a trade secret, although testing using their acrylate series was suggested; however, all acrylates were negative in our patient. The medical-grade adhesive was also found on the nonwoven carrier tape, which she did not react to. The patient only reacted to the square padded poly­urethane foam, suggesting that this was the likely culprit. No information was provided regarding the components of the poly­urethane foam, although the company indicated that the adhesive may contain trace amounts of solvents, which are evaporated during the raw material conversion process and are present only in minimal quantities in the final product. In the UK, available patch test units include IQ Ultra and IQ Ultimate from Chemotechnique Diagnostics, Finn Chambers from SmartPractice, Van der Bend patch test chambers (which use aluminium cups and discs) and TRUE Test, a hydrogel film with preprepared allergens for rapid screening. Contact allergy to patch test units or chambers is very rare, as these are made from hypoallergenic materials, although we present this case to highlight the possibility of this occurring in select patients.