The skin patch test is a medical test, which is conducted to determine if you are experiencing allergic reactions to certain substances. As the name suggests, to conduct this test a patch of skin is exposed to the potential allergy-causing substance. After that, your skin needs to be observed for the next 48 hours or so for any allergy symptoms. This test (along with your medical history) can help you confirm if a particular substance you touch could be triggering off allergic reactions.
The main reason to undergo a skin patch test is to find out if there are any allergens you need to stay away from. This test could also be useful for diagnosing certain skin problems such as contact dermatitis and latex allergy. Your doctor may advise you to go in for a skin patch test in case you break out into a rash quite often for no apparent reason.
Before conducting the skin patch test, your doctor will ask you to discuss your medical history as well as the symptoms you have been experiencing in detail. This includes previous skin diseases, treatments undergone, general health, cosmetics and toiletries you use, occupational exposure to chemicals or metals and your hobbies.
In case you are taking any medication, you may be asked to discontinue doing so for a while.
The skin patch test is a non-invasive one, in which the doctor will not even need to use a needle. However, it needs to be conducted on a skin site where the dermatitis isn’t apparent.
A small amount of the potential allergen is mixed with some non-allergic material, to prepare a suitable concentration. Your skin may be exposed to around 20 to 30 extracts of different substances, which could cause contact dermatitis. These include latex, fragrances, dyes, resins, metals, preservatives and medication.
The concentrated allergen is applied on to small aluminum discs, which are secured to your upper back area, with the help of adhesive tapes. The test sites are marked carefully.
You will need to wear the patch in place for around 48 hours or so. During this time, you need to avoid any activity that can cause you to sweat heavily. Do not expose the patches to sunlight or any other type of UV light. You may also need to avoid bathing or exposing your skin to water while the test is being conducted.
At the end of 48 hours, you need to return to your doctor, who will remove the patch and examine your skin. After an hour of removing the patch an initial reading will be conducted. The final reading will take place 48 hours after removing the patch. You need to refrain from washing the area until the final reading is over.
The reactions seen on the skin are scored as per the International Contact Dermatitis Research Group System, which is -
Reactions that are evident the day the patch is removed are called irritant reactions. Allergic reactions could take up to 5 days to appear.
Though uncommon, certain complications have been known to occur due to the skin patch test. These include -
It is absolutely essential to consult a doctor in case you notice any of these side effects.
The cost of the skin patch test varies between US$ 400 and US$ 600. You could claim some of it from your insurance company if it is being performed for medical purposes. Speak to your doctor and insurance provider before making a claim.
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