Allergy testing is a first step. It can help your child get a diagnosis (of course, it may not be allergy). Then you and your regular doctor or allergist can make a plan, starting with what allergic triggers to avoid and how to avoid them.

Hopefully that means your child has fewer symptoms. If not, they'll be able to get the antihistamine, corticosteroid or any other relief they need when they need it. Some allergy medications may actually be more helpful if taken to prepare for contact with the trigger. For instance, that could be before your child’s pollen season starts or when they’re about to visit someone who has a dog or cat.

Allergy immunotherapy may be an option too. This long-term treatment aims to reduce children’s symptoms, and need for medication, by retraining their immune system. It’s available for some allergies and children usually need to be at least 5 years old.

How your child reacts in an allergy test can sometimes be a helpful clue to how their condition might develop. For instance, a strongly positive result tends to suggest kids are less likely to grow out of a food allergy. Testing can also lead to a full diagnosis for young children who are allergic to one food and may later react to others.

Meanwhile early sensitization to cow’s milk, chicken eggs and allergens you breathe in may increase the risk of later developing asthma. Treating allergies early may help lower the risk.

There are three main types of allergy testing for kids (and grown-ups):

• Skin tests – different types of test for different allergic conditions
• Blood tests – useful for children with a skin condition that may interfere with a skin test
• Challenge tests – exposes your child to their possible trigger, usually a food or medication

Allergy blood tests look for Immunoglobulin E (IgE) antibodies in your child’s blood. Skin tests and challenge tests look for a reaction as evidence of their presence.

The immune system makes the antibodies as protection against substances it thinks are a threat. Sometimes it gets it wrong. Pollen, animal dander, dust mites, peanuts, latex, even insect stings are generally harmless. But if you have an allergy to one of them, the antibodies set off a reaction to expel it from your body as fast as possible.

A positive result shows your child is sensitized to a particular substance. It doesn’t necessarily mean they have an allergy. And here’s why.

The first contact with an allergen programs your child’s immune system. It produces IgE antibodies and their body is ready to react if they meet it again. But not everyone will develop allergy symptoms even though they carry the antibodies and test positive. This is known as being sensitized but not allergic.

We should also say that false positives and false negatives are possible with allergy tests. That’s why you need your doctor or allergist to interpret and confirm the results.

Test results can help narrow down the list of possible triggers because IgE antibodies are specific to a substance or allergen. But they’re only one piece of the puzzle. Be ready to answer questions about your child’s symptoms, from runny nose to skin rashes and everything in between. An allergy diary can be a useful way of keeping track:

• What symptoms your child experiences
• When allergy symptoms started
• How long they last for
• How badly they affect your child
• Times of the year or places that make symptoms worse
• What you think might be the trigger

If you have relatives with allergies, that’s important information too because allergy tends to run in families.

What kids actually feel during an allergy test and how they feel about it will vary. Talk to them beforehand so they know what to expect.

This tends to be the first choice of test. It’s also called a prick test, scratch test or percutaneous test. Skin prick tests can help identify allergies to different allergens such as pollen, dust mites, animal dander, mold or latex. Food allergies are complex and may require additional tests. Skin prick testing is used for penicillin allergy. It’s less reliable for other drug allergies where a negative result may not be conclusive.

A drop of liquid containing an allergen is placed on your child’s arm. The skin is then gently pricked and checked for a response about 15 minutes afterwards. A small red swelling (wheal) like a mosquito bite shows your child may be sensitized to that substance depending on the wheal size. Little children often can’t resist itching so may have the test on their back.

The next step after a negative or inconclusive result may be an intradermal test.

This is normally done to identify non-IgE allergies causing skin inflammation (contact dermatitis). Patch tests can be for triggers like metals, chemicals and medications. It involves taping small patches carrying the allergens to your child’s arm or back. The reaction can take 48 hours or more after patch testing to show. 

Your allergist may suggest a blood test if your child needs to keep taking medications that could interfere with a skin test. Also if they have particular skin conditions. Or have ever had a severe allergic reaction. The sample goes off to the lab so it may be quite some time before you get the allergy test results.

This involves taking a small blood sample from your child’s arm or with a finger prick. The lab looks for specific IgE antibodies in the blood indicating sensitization. Finger pricks and needles are no one’s favorite thing. Children may be able to have numbing cream before allergy blood tests taken from their arm. That’s as long as they’re not allergic to lidocaine.

It's a variation of the allergy blood test taking a more detailed look at the triggers. There may be several proteins in a substance that can cause allergy symptoms. A component test can tell you which one your child is sensitized to. That’s helpful if they react to peanuts, tree nuts or insect venom because some proteins in these allergens are more likely to set off a severe reaction.

This can help to confirm or rule out allergy in a child with a rash after taking a medication, often an antibiotic. The doctor or nurse starts by giving a small dose. The challenge then builds up step by step as long as there’s no sign of a reaction. Kids who can’t take the oral medication may have injections instead.

One test we haven’t mentioned yet is a breath test or lung function test (spirometry). It could be part of the initial physical exam for children who already have asthma symptoms like a tight chest or wheezing. The test involves blowing into a tube connected to a computer. Typically, the child repeats the test after inhaling medication to open their airways. If there’s an improvement in their breathing, that’s another clue to guide the diagnosis and treatment plan.

The doctor or nurse will explain what’s going to happen but children may find the process a little scary. Tell them astronauts do the very same test.

Common types of allergy testing for kids include different skin tests, blood tests and challenge tests. Children may need more than one to rule allergy in or out as the cause of their symptoms. Your doctor or allergist will interpret the results alongside your child’s detailed clinical history and symptoms.

The whole process of allergy testing for kids may seem daunting. But it can unlock the right treatment for your child’s allergy.

Last medically reviewed on 8 August 2023