Skin prick test

What is it?

Skin prick tests are helpful in diagnosing immediate (IgE-mediated) allergic reactions to foods. Skin prick testing involves pricking the skin with a specialised device that is coated with a small amount of the allergen to be tested. The test is then measured after 15 minutes. A test is considered positive if a wheal (hive) reaction occurs at the test site.

What do the results mean?

The size of the skin prick test correlates to the probability an immediate allergic reaction to the food tested.

Does it predict the risk of anaphylaxis?

A child with a “high positive” skin test result is not more likely to develop anaphylaxis; similarly a child with a “low positive” skin test result is not less likely to develop anaphylaxis.

The risk of anaphylaxis is difficult to predict, and is likely to depend on several factors, including: a) past anaphylaxis, b) amount of food allergen ingested, and c) presence and severity of co-existing asthma.

Are there any risks involved?

Skin prick tests are safe. It is common to have skin itch and redness around the area tested, which usually resolves within 24-48 hours. The risk of anaphylaxis is very low (approximately 1 in 3000 patients or 0.03%), and it will be promptly managed if it occurs.

How is my child positioned?

The child sits down facing the parent, straddling his/her legs on each side of their legs, hugging them under their armpits. The parent firmly holds the child’s arms (between the elbow and shoulder), bringing the child’s head and body snugly against the parent’s chest.

Marks are drawn on the child’s back with a pen where the skin prick tests are then performed.

What should I tell my child to expect?

Tell your child that the skin prick tests feel “prickly” so it can be uncomfortable. Reassure them that although it can feel a sore, sharp or painful, majority of children find it just itchy, annoying and sometimes even ticklish.

Do warn them that after the test is performed their back becomes very itchy, but it is important to not scratch while waiting for the next 15-20 minutes
It would be helpful to bring a toy/activity book to distract them with during this time

Let them know they will return to the doctor to have their skin tests measured with a ruler, and it is unlikely to have any repeat scratches, unless further discussed.