Diagnosis of allergic contact dermatitis is based on the appearance of the lesions. Tests e. g. potassium hydroxide fungal culture are important in ruling out tinea species as a cause. The patch test may be used to identify which allergen, usually chemical, you are allergic to. It is cost effective and allows you to identify the allergen and so avoid it as an aid to treatment. Skin biopsy helps in excluding other causes.
Attribution: Avallain