Patch Testing For Skin Allergies

An allergy skin test is used to identify the substances that are causing your allergy symptoms. It is often performed by applying an extract of an allergen to your skin, scratching or pricking the skin to allow exposure, and then evaluating the skin's reaction.

A Patch test for skin allergies is one of the methods used to test for skin allergies. It involves applying an allergen to a patch which is then placed on the skin.

This may be done to pinpoint a trigger of allergic contact dermatitis. If there are allergic antibodies in your system, your skin will become irritated and may itch, much like a mosquito bite. This reaction means you are allergic to that substance.

Patch testing should be done on a skin site where the dermatitis is not apparent.

The allergens are mixed with a non-allergic material (base) to a suitable concentration. They are then placed in direct contact with the skin, usually on the upper back, within small aluminum discs. Adhesive tape is used to fix them in place, and the test sites are marked.

The patches are left in place for 48 hours, during which time it is important not to wash the area or play vigorous sport because if the adhesive tapes peel off the process will have to be repeated.

When do you need Patch testing for skin allergies?

Dermatologists apply patch tests in patients with dermatitis, to find out whether their skin condition may be caused or aggravated by a contact allergy.

If you have a dermatitis that started recently or if you have a persistent or unusual eczema, your dermatologist may suspect you have an allergic contact dermatitis. If you have been using a medication on the lower legs, hands, face, ears, eyes, anal or genital region for a while and subsequently developed dermatitis, your doctor may suspect that this is aggravating the dermatitis.

Patch testing is the only way that your doctor can prove that a substance is causing or aggravating your dermatitis. Once an allergen is identified, avoiding it should help cure your dermatitis.

Some of the common allergens that are tested include:

• Caine Mix,
• Carba mix,
• Cobalt,
• Epoxy resin,
• Blasam of Peru, and
• Formaldehyde

Patch tests do not always explain the cause of dermatitis.

What are the Risks in Patch testing for skin allergies

Although small amounts of allergens are introduced to your body, the skin patch test is relatively safe.

The biggest risk with allergy skin tests is the possibility of anaphylactic shock, a potentially life-threatening condition.

Anaphylaxis is a rare, severe allergic reaction that involves two or more body systems. It often begins immediately after an individual has been exposed to a particular allergen. Without prompt emergency treatment, anaphylaxis may progress to anaphylactic shock, which is characterized by difficulty breathing and a dangerous drop in blood pressure. An emergency dose of epinephrine (adrenaline) is necessary to reverse these symptoms.

However, after performing a patch test for skin allergies, you should contact your medical provider the moment you get any of the following symptoms:

• Fever,
• Lightheadedness,
• Wheezing,
• Shortness of breath,
• Extensive rash,
• Swelling of the face, lips or mouth, and
• Difficulty swallowing.

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