The necessity of a test reading after 1 week to detect late positive patch test reactions in patients with oral lichen lesions

Abstract

Establishing the clinical relevance of contact allergy to dental materials in patients with oral lichen lesions (OLL) may be difficult, and tests are often read only on day 3 or day 4; also, concentration of the tested allergens may vary. Several studies on dermatitis patients have shown that additional positive patch test reactions can be found after day 4. Therefore, the aim of the present study was to analyse the frequency of late positive reactions to potential allergens in patients with OLL. Eighty-three of 96 consecutive patients with biopsy-verified OLL were patch-tested with a recently developed lichen series. The patches were removed after 48 h and reactions read 3 and 7 days after application. A total of 129 contact allergies were found, and 26 (20.2 %) of the allergic reactions in 23 patients were seen on day 7 only. The 25.2 % increase in positive test reactions with an additional reading on day 7 in addition to day 3 was statistically significant. Metals were the substances with the highest frequency of late positive reactions. Patients with OLL cannot be considered properly investigated with regard to contact allergy, unless the testing has been performed with mandatory readings on day 3 (or day 4) and day 7. Late patch test readings are crucial in order to elucidate the role of contact allergy to dental materials in the aetiology of OLL.