Piroxicam has at least two epitopes for contact photoallergy

Thimerosal [MAK Value Documentation, 2001]

“…However, one week after sensitization, 9/10 and 8/10 animals photosensitized with piroxicam reacted in the patch test to 1 % thimerosal or thiosalicylic acid, also without exposure to light, but none of the 10 animals reacted to 1 % piroxicam without light (Ikezawa et al 1992). Similar results, but for a smaller number of animals, were described in another study (Hariya et al 1993).…”

Photoallergy

“…The most positive reactions to etofenamate in EMCPPTS were found to have limited clinical relevance, thus raising the question of phototoxicity rather than photoallergy (28). Other NSAIDs are reported to cause photoallergy like piroxicam, benzydamine, diclofenac, and others, and some are listed in Tables 3 and 4 (43,68,76,(104)(105)(106)(107)(108)(109)(110)(111)(112).…”

Induction of eosinophil-infiltrating drug photoallergy in mice

“…Various drugs have been reported to induce photosensitivity, including quinolones [3], afloqualone (AQ) [4], piroxicum [5], non-steroidal anti-inflammatory drugs [6], and others. There are phototoxic [2] and photoallergic [3][4][5][6][7] mechanisms in drug sensitivity, and the incidence of photoallergy is higher than that of phototoxicity [3]. Two theories of photoantigen formation have been put forward to explain the photoallergic mechanisms, prohapten and photohapten [8].…”