Why is a
A challenge procedure definitively determines if your child is or isn’t allergic to the particular food or challenge. Your doctor may have ordered the challenge test for a variety of reasons, most commonly because:
Your child never eaten the food, but have had a skin test which is positive to the food
Your child has previously had an allergic reaction to the food, but now the skin test is lower and they may have outgrown their allergy
Your child may be allergic to fresh milk or whole egg, but potentially tolerant to small amounts of baked egg or baked milk in a cake/muffin
How is a
How is a challenge performed?
Your child will have their challenge performed under medical supervision in a clinic setting. This usually involves your child coming in for approximately 3-4 hours either in the morning (8.30am-12.30pm) or afternoon (12.30-4.00pm).
Your child will generally be looked after by an specialist allergy nurse, and initially a very small amount of the food (e.g. 1/8 of a teaspoon of peanut butter) will given. If this is tolerated, then the dose is gradually increased every 15-20 minutes until a full serve (e.g. 2 teaspoons of peanut butter) is given
What are the possible
Outcomes of a Challenge?
There are two usual outcomes, and that is
- Your child has an allergic reaction – in which case usually antihistamine (e.g. Zyrtec) will be given to make your child feel better, or
- Your child is tolerant to a full serve – in which case your child will then continue eating the food on a daily basis for the next 7 days. After 7 days, a nurse will contact you (to confirm that no reactions has occurred at home) to confirm that your child remains tolerant to the food.
Is a Challenge?
Very safe. We are very careful with performing our challenge procedure, initially through careful selection. We reduce the chances of a severe reaction occurring by ensuring your child is well at the time of the challenge, and has had no troublesome asthma.
As the challenge is conducted through slow administration of initially small quantities of the food or antibiotic, majority of allergic reactions (90-95%) are mild, consisting of hives, lip swelling, abdominal pain.
If your child has an allergic reaction, the chances of anaphylaxis (difficulties breathing, throat tightness, persistent coughing) are low, typically between 5-10%. If anaphylaxis does occur, majority will require only a single dose of an adrenaline injection.
What happen when my child has been
Deemed to passed a Challenge?
We will write a letter to your referring doctor to inform them that your child has passed the food or antibiotic challenge. If your child has passed a food challenge test, we recommend that they now incorporate the food into the diet as part of the regular diet, typically 2-3 times per week or whatever is practical.
Regular ingestion of the food may help ensure that tolerance is maintained and that the body “remembers” that the food is OK.
Skin Prick Test
A Skin Prick Test?
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
The size of the skin prick test correlates to the probability an immediate allergic reaction to the food tested.
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.
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.
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.