How is allergy testing done and does every child need to do it?
Allergy testing can be quite nuanced and vary from scratch testing, to blood work, to observed food challenges.
Not every child requires allergy testing. What type of testing is recommended depends largely upon the clinical history and severity of the reaction. Family history should also account for decision making on allergy testing. Infants with two or more allergic family members are at a higher risk of allergy themselves.
Patients who are atopic are also at a higher risk of allergy. Atopy is a hypersensitive immune response to certain triggers. Asthma, eczema, and allergies make up the atopic triad, meaning they tend to co-occur. For example, those who have eczema may be more predisposed to food, seasonal, or environmental allergies. It may be clinically relevant to figure out through formal allergy testing, the causative triggers that may exacerbate these allergic symptoms.
Babies that have rough, scaly, atopic dermatitis in infancy are at higher risk of developing food allergies. If the condition occurs before 6 months of age this puts them at even higher risk. For patients with moderate to severe atopic dermatitis, I recommend allergy testing prior to the introduction of highly allergenic foods such as peanuts, eggs, tree nuts, and milk. The recommendations about when to introduce highly allergenic foods has changed drastically over the course of the past decade. It was previously thought that we should wait on these foods until children are older; but we now know that early introduction has a protective benefit and helps the immune system adapt to the agent and induce greater tolerance to certain foods. For a child with severe eczema, ruling out food allergies early can help guide the early introduction of these foods and bolster the protective benefit of early immune introduction.
If your child has had an allergic reaction to a highly allergenic food, it is advised to hold off on further introduction of other allergens until formal allergy testing is conducted. If an allergic reaction occurs with food introduction, even if it may be mild, it should be disclosed to your pediatrician because further testing may be recommended.