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An allergy test can determine whether eating, breathing or touching a certain substance (called an allergen) is contributing to your child’s symptoms. Information found during an allergy test can help your child’s doctor determine whether an allergy is present and which allergens your child might need to avoid. Allergy testing can also help determine whether your child’s life-threatening reaction to a bee sting would require allergy injections to protect him or her.
An allergy test can determine whether your child has an allergic condition or reaction caused by:
Allergy tests look at whether an allergen may be causing your child’s symptoms by testing for a specific antibody that is made against that allergen. Allergic reactions cause an antibody called immunoglobulin E (IgE) to form. The immune system normally uses antibodies to identify foreign invaders like bacteria and viruses—a normal protective immune response. The IgE antibody works differently: It causes an exaggerated response.
When allergies occur, the IgE antibody latches onto cells in the body—often around blood vessels, airways, the digestive system and the skin. Allergy tests look for the presence of the IgE antibody that is responding to specific allergens.
An allergy testing appointment at Riley at IU Health usually takes about 40 minutes, though it can take longer depending on your child's medical history. It is important that your child not take any antihistamines for one week prior to the appointment.
To choose the appropriate allergy tests and confirm a diagnosis, your child’s allergist will review your child’s medical history and perform a physical exam. A positive allergy test by itself does not make the diagnosis. The doctor must decide if your child’s signs, symptoms and history are consistent with allergy.
During the test, your child will be asked to lie flat on an exam table on his or her stomach with his or her back exposed. A member of the clinical team will use alcohol to clean the skin on your child’s back before making a series of marks with a pen or marker. These marks serve as a map for the area of skin being tested for each specific allergen. The number of tests your child's allergist performs depends on your child’s medical history.
Next, a member of the allergy team will use a small device called a probe to apply a small sample of each allergen being tested. The probe quickly pricks the skin, and while it does not cause bleeding, it may cause some mild discomfort. Once all allergens have been applied, your child will need to keep lying on his or her stomach for another 15 minutes.
After 15 minutes, the allergy specialist will examine the areas to determine whether any of the allergens caused a reaction and then score the tests. The doctor will share the results with you and your child and discuss whether environmental changes, dietary changes or medicines will be needed to manage his or her symptoms.
The best way to treat an allergy is to avoid the allergen. The doctor may also recommend treatments like immunotherapy or allergy shots if it is not possible to avoid the allergen.
There are three types of allergy tests:
Doctors score allergy tests in many ways. The important thing to note is that the score does not measure how severe the allergy is in the patient. Severity of the allergy is based on the type of reaction caused by the allergen. For example, your child might have a low score on the test but experience anaphylaxis in reaction to the allergen. Alternatively, your child may have a high score on the test and experience only a mild skin reaction. Your child's allergist uses test results to determine only if there is or is not sensitivity to the allergen.
In addition, an allergy test may result in a false positive, which means that the test shows sensitivity but your child does not experience any clinical reaction. The test only shows that an IgE antibody is being made. Therefore, allergy tests are an important part of the diagnosis, but they must be considered with many other things like your child’s medical history and history of exposure to allergens to confirm both the diagnosis and the severity of an allergy.
Parents are often told that their children are too young for allergy testing, but this depends on the type of allergy being tested.
In children, the first allergies to cause reactions are food allergies. These can show up as atopic dermatitis (skin irritation). This illness may appear after a child turns 3 months old. Doctors may order an allergy test for infants with dry, itchy, flaky skin who are older than 3 months old to help determine if a food allergy is causing the skin irritation. Other food reactions that can be seen at an early age include anaphylactic shock, hives, vomiting and diarrhea.
On the other hand, testing very young children for pollen allergy is not necessary. This is a frequent concern of parents of children with nasal symptoms or allergic asthma. The development of pollen allergy takes time. It evolves over two to three seasons. There may be other airborne allergens that would be more pertinent, such as house dust mites or cat or dog dander. These are more perennial allergens that can lead to symptoms in a young child with only a year of exposure while pollen allergy takes a few years to develop.