Patch testing is a form of skin testing used to determine the cause of allergic contact dermatitis. Small disks or chambers containing different chemicals are taped to a patient’s back for several days. Small areas of localized inflammation may appear within 2-4 days, or even up to a week, and confirm the presence of sensitivity to a variety of substances, including metals, rubber compounds, fragrances, preservatives and sometimes medications. This form of testing is looking for delayed skin reactions, also called type IV hypersensitivity reactions, and helps the provider determine if a person’s skin inflammation is due to contact with something in their home or work environment. Patch testing is different from skin prick testing and is not used to diagnose immediate or acute hypersensitivity to foods and other allergens.
Find out more about allergy testing.