A patch test is a method used to determine whether a specific substance causes allergic inflammation of a patient’s skin. Any individual suspected of having allergic contact dermatitis might needÂ patch testing, if the exact cause is difficult to determine.
Patch testing helps identify which substances may be causing a delayed-type allergic hyper sensitivity reaction in a patient, and may identify allergens not identified by blood testing or skin prick testing. It is intended to produce a local allergic reaction on a small area of the person’s back, where the diluted chemicals areÂ placed. The chemicals included in the patch test kit are the offenders in approximately 85â90 percent of contact allergic eczema, and include chemicals present in metals (e.g., nickel), rubber, leather, formaldehyde, lanolin, fragrance, toiletries, hair dyes, certain topical medications, adhesives, preservatives, and other items.