Patch testing is generally done to see whether a particular substance is causing allergic skin inflammation (contact dermatitis). Patch tests can detect delayed allergic reactions, which can take several days to develop.
Patch tests does not require needles. Instead, allergens are applied to patches, which are then placed on your skin. During a patch test, your skin may be exposed to 20 to 30 extracts of substances that can cause contact dermatitis. These can include latex, medications, fragrances, preservatives, hair dyes, metals and resins.
Patients wear the patches on your arm or back for 48 hours. During this time, you should avoid bathing and activities that cause heavy sweating. The patches are removed after 48 hours and patients return to our office after 72 hours for a skin reading. Irritated skin at the patch site may indicate an allergy.