Skin Testing to Determine Allergies

Skin testing for allergies is a time-tested and easy procedure. Follow along on this pictorial to see the process unfold on a young patient.

1

Preparing the Skin for Testing

Skin testing is often performed on a person's back or forearm. The test starts by cleaning the skin with rubbing alcohol. — Daniel More, MD

The skin is prepped for testing by allergy testing with rubbing alcohol, typically on the back or arm.

2

Skin Testing Devices

There are many skin testing devices for allergy testing. Many perform multiple skin tests on a single device. This is a multi-headed skin test device that allows five skin tests to be placed at once. The device has a small metal point that is dipped into allergen extracts, then pushed into the skin.

3

Marking the Skin

The skin is marked with a surgical marker in order to keep track of which skin test site represents which allergen.

4

Ready for Skin Testing

Skin is ready for testing. Young patient/ — Daniel More, MD

The skin is now ready for allergy tests to be placed.

5

Skin Testing Procedure

Puncture of skin with allergens — Daniel More, MD

The skin test procedure involves gently pressing the skin test device into the skin, with metal or plastic tips puncturing just the top layer of the skin. This causes the allergen extracts to enter the top layer. This form of skin testing is termed "puncture," which is a variation of the scratch or prick test. Skin testing is not painful.

6

Completing the Skin Test

The skin testing method is repeated until all skin tests have been placed. — Daniel More, MD

A number of skin tests are placed, depending on the symptoms of the patient and what the allergist to trying to determine are the possible causes of the person's allergy symptoms. Depending on the age of the person and the reason for testing, this may range from 10 to 70 or more skin tests.

7

Blotting the Skin

Blotting excess allergen — Daniel More, MD

Excess allergen extract is removed from the skin by blotting with paper towels. This is so that the liquid will not run into adjacent skin testing sites, causing false reactions.

8

Waiting 15 Minutes

Once the skin tests have been placed, the results will be complete after about 15 minutes. Reactions may develop sooner. — Daniel More, MD

A timer is set for 15 to 20 minutes, allowing time for the skin tests to react prior to reading the results. They may not take that long to react.

9

Reading the Results

Positive test results show wheals and bumps. — Daniel More, MD

The skin test results are read at 15 minutes. A positive test shows a wheal (bump) and flare (redness) reaction. These are measured and compared to the positive and negative controls. The size of the reaction determines whether the test is positive or negative.

10

Close-up of Results

The wheal and flare reaction may be of unusual shapes, indicating a strong reaction. — Daniel More, MD

A close-up of the results shows a significant positive reaction to an allergen as a result of skin testing. The site may be very itchy, but the rash and itching will go away without treatment within an hour or so. The wheal and flare reaction may be of unusual shapes, indicating a strong reaction.

11

Skin Testing Complete

Skin testing is now complete, and the patient is able to leave. — Daniel More, MD

The skin test is now complete and the results can be interpreted by the allergist. Some allergists recommend that the patient remains in the clinic for up to 30 minutes to ensure that unexpected side effects do not occur. Side effects from skin testing are extremely rare.