SKIN TESTING FOR ALLERGIES – BASICS

What is an allergy?

An allergy is an abnormal reaction from an immune response to something that comes in contact of skin or inhaled, or ingested in body. Allergic reactions can lead to sneezing, wheezing, coughing, itching, skin rashes, swollen face or tongue, stomach pain, diarrhea etc.

Why is skin-testing for allergies done?

Skin-testing is a method that doctors use to see whether a patient’s exposure to specific substances provokes an allergic response. Extracts (i.e. material used for allergy testing) are made from common allergens like various plant source (e.g. grass, trees, and pollen); mold spores; animal dander; cockroach or dust mite debris and certain foods.

What common methods are used for skin testing?

• Per-cutaneous (“Prick”) Method: A drop of each allergen extract is placed on the skin, either the lower arm or back. Then, pricking, puncturing, or scratching lightly breaks the topmost layer of skin under the drops. This pricking allows the extract to go below into the skin.
• Intradermal Method. The allergen extract is injected under the first few layers of skin using a very thin needle.

Prick skin-testing is usually not painful but can cause some discomfort as the allergen is injected. It may also cause some itching for some time.

How many allergens are usually tested at once?

Depending on a particular patient’s history, anywhere from 10 to about 50 different allergens are tested.

What do the results of the skin test mean?

After the allergen extracts are placed on the skin, doctor looks for signs of an allergic response. A positive response appears in the form of a raised bump or wheal, surrounded by a red area, or flare.

Usually, with a prick test, the raised area should be at least three millimeters to indicate a positive reaction. With an intradermal test, even larger reaction is required.

A positive test does not necessarily mean that you will have allergy symptoms when you are exposed to that allergen, or that the allergen is a cause of your symptoms. This is one reason why your skin test results need to be carefully correlated with your history by an experienced doctor or allergy specialist to determine appropriateness of results.

How to prepare for skin-testing?

For proper allergy testing, all antihistaminic drugs (e.g. Tab Avil) should be stopped for five to seven days prior to skin-testing. You can continue to take any nasal steroid sprays and asthma medicines as per doctor’s advice.

Who should get skin-testing?

Skin-testing is useful for anyone who wants or needs to identify specific allergy triggers. Anyone, regardless of age, can be skin tested for allergies.

What happens if the skin test is positive for allergies?

The allergens which trigger allergy reaction during skin test can help doctor to educate you about how to avoid exposure to possible allergens. It can also help create a treatment plan to address your specific symptoms. For instance, if you are allergic to substances such as dust mites or pollen , you can take steps to limit your exposure to them.

Are there any possible side effects to skin-testing?

Rarely patients may develop allergic reactions to skin-testing such as severe itching or wheezing, so testing should be performed in a facility capable of treating a reaction if it occur.