Clinical Dermatology > Dermatitis
These tests to identify causes of allergy consist of applying 30 substances to small aluminum blades, which are fixed to the patient’s back for 48 hours. When they are withdrawn, it takes another 48 hours to make the diagnosis because there are late allergies that take time to manifest. If the patient has developed an allergy to some of the 30 substances tested, the skin of the site that was in contact will have a reaction.