The patch test (epicutaneous test) and photo patch test are used to clarify the etiology and diagnosis of allergic as well as light-potentiated contact der matitis. The patch test must be correlated with historic data and physical ex amination. Contact dermatitis constitutes a significant proportion (5%-15%) of the dis eases at dermatologic clinics. If the results are to be reliable, patch tests should be performed properly and the technique should not be varied in an arbitrary manner. The examiner should adhere strictly to the standard procedure so as to understand its possibilities and its...