Skin and RAST Testing

Skin test applicator.
Skin test applicator.

Skin testing is a relatively painless procedure that involves applying potential allergen drops to your skin using a plastic panel of 8 prongs. This is called intracutaneous skin testing. The panels can be applied either to the forearms or with a young child on their back. They include food and/or environmental allergens identified by you and the provider.


Skin testing.
Skin testing for allergies.

The drops then sit on your arms or back for 10-15 mins. If you are allergic a wheal and hive will develop along with itchiness. The skin tests are read and wiped clean after 15 mins. Benadryl Spray may be applied to diminish any itching.


Skin test results.
Skin test results.

For older children and adults intradermal testing is also done usually on the triceps region of your arm. The allergenic substance (only environmental allergens) is then injected under the first layer of your skin using a tiny needle. The patient waits 10-15 mins and the skin tests are read. Both forms of skin testing allow us to get a complete picture of what allergens may be bothering you.


RAST (ImmunoCap Rast) is blood testing that can also be done to check for food or environmental allergies. This form of testing is used in situations where there is not clear clinical evidence of a food allergy and skin testing may be inconclusive. In moderate to severe eczema/hives it may not be possible to skin test the patient without getting falsely positive results. In this case blood testing is done to either confirm suspected allergens or to rule out possible allergens. We will also consider blood tests for those patients who can’t discontinue antihistamines for 5 days prior to the testing.