system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Patch testing is done for -
assistant
The correct answer is  patch testing is the only scientific method to detect the cause of alergic contact dermatitis. patch test consists if allergens in petrolatum in proper concentration applied in cups and fixed with a tape to the upper back for 48hrs. the reading is taken after 48hrs, 72hrs and after 1 week if the test is positive the raection site produces vesicles ,bulle or erythematous papules. IADVL TEXTBOOK OF DERMATOLOGY, CONTACT DERMATITIS PAGE 581