WHAT IS PATCH TEST?
WHAT IS THE PROCEDURE [METHOD] FOR PATCH TESTING?
Patch test [patch testing or skin allergy test] helps in identifying which substances may be causing an allergic reaction in a patient. A patch test is a method used to determine whether a specific substance causes allergic reaction in a patient's skin.
Patch test is a specialised procedure done in a dermatologist's clinic. In a patch test procedure, very small quantities of 20 or more testing materials [allergens] are added to aluminium chambers and these chambers are applied to the upper back. These chambers are kept in place with special adhesive tape.
The patches stay in place for at least 48 hours. Shower [getting the back wet during patch testing] must be avoided. Vigorous exercise or stretching should also be avoided.
The patches are usually removed after 48 hours[in the dermatologist's clinic]. The back is marked with a marker to identify the test sites and a reading is taken. These marks must be visible during the next visit and another reading is taken 24 to 48 hours later.
Then results are recorded for each test site e.g. negative, irritant reaction, weak positive, strong positive etc.
WHAT ARE THE MOST COMMON ALLERGENS?
Nickel is the most common allergen. Nickel allergy is more common in young women as they wear jewellery made of nickel e.g. ear rings coated with nickel, watch, belt, zipper or jewellery etc.
Other common allergens include fragrance mix, neomycin, formaldehyde, and cobalt.
The chemicals included in the patch test kit are the culprits in approximately 80 to 90% of allergic contact dermatitis cases. These include metals e.g.nickel, rubber, leather,formaldehyde,lanolin, fragrance, toiletries, hair dyes, medicines, pharmaceutical items, foods, drink, preservatives, and other additives.
A positive patch test might not explain the present skin problem, because the test only indicates that the individual became allergic during encounters with that chemical at some point in their life.
WHERE IS SKIN PATCH TEST FOR ALLERGIES AVAILABLE?
Patch Test Services are available at a Dermatology Clinic and it is one of the most commonly performed diagnostic procedures.