Allergy Testing for Children: What the Process Looks Like

When allergy testing is considered

A pediatrician or specialist may suggest allergy evaluation when a child has: - Recurrent or persistent nasal symptoms, itchy eyes, or sneezing not explained by infection - Asthma that is not well controlled or that flares with suspected allergens - Repeated hives or angioedema (deeper swelling) with no clear explanation - A reaction to a specific food, insect sting, or medication that raises concern for allergy - Moderate-to-severe eczema that has not responded to skin-care measures alone

Testing is not necessary for every cough or every runny nose. The allergist decides which tests make sense based on the history rather than running a broad panel 1Ref 1Sicherer SH, Wood RA; AAP Section on Allergy and Immunology (2012).Allergy Testing in Childhood: Using Allergen-Specific IgE Tests.Indications for allergy testing in children, how to interpret IgE tests, and when results must be paired with the clinical history to be meaningful. A positive test result does not always equate with clinical allergy — a direct correlation cannot be assumed between the presence of specific IgE antibodies and actual allergic symptoms in the child's daily life.

Skin-prick testing: what happens

Skin-prick testing is the most common first-line method for environmental and food allergens. A small amount of purified allergen extract is placed on the forearm or upper back, and the skin beneath each drop is lightly pricked with a small device — the prick is superficial and does not draw blood. A positive result is a small raised wheal (like a mosquito bite) at the allergen site after about fifteen minutes; a reaction is considered positive when the wheal diameter is at least 3 mm greater than the negative saline control 2Ref 2Boyce JA, Assa'ad A, Burks AW, et al.; NIAID-Sponsored Expert Panel (2011).Guidelines for the Diagnosis and Management of Food Allergy in the United States: Summary of the NIAID-Sponsored Expert Panel Report.Skin-prick test methodology, wheal size threshold for positive result, and patch testing for contact allergens. Controls (a positive histamine drop and a negative saline drop) confirm the test is working. The test can evaluate dozens of allergens in one visit and results are available in the office. Most children over about two years tolerate it well. Antihistamines must be stopped several days before testing because they suppress the skin reaction.

Blood tests (specific IgE)

A blood test measuring IgE antibodies to specific allergens is an alternative or complement to skin testing 1Ref 1Sicherer SH, Wood RA; AAP Section on Allergy and Immunology (2012).Allergy Testing in Childhood: Using Allergen-Specific IgE Tests.Indications for allergy testing in children, how to interpret IgE tests, and when results must be paired with the clinical history to be meaningful. It does not require stopping antihistamines and is preferred when a child has a skin condition like severe eczema that covers too much skin for reliable prick testing, when a child is taking medications that cannot safely be stopped, or when there are concerns about rare severe reactions during the skin test procedure itself. The result is reported as a level (a number and a class), but higher numbers do not reliably predict more severe reactions. A positive blood test for a food allergen in a child who has never reacted to that food does not automatically mean the child will react — this is a common source of confusion and over-restriction.

The oral food challenge

When the history and test results are ambiguous — for example, a positive skin test for a food the child has eaten without obvious reactions — an oral food challenge (OFC) is the most accurate way to determine whether a clinical allergy exists 1Ref 1Sicherer SH, Wood RA; AAP Section on Allergy and Immunology (2012).Allergy Testing in Childhood: Using Allergen-Specific IgE Tests.Indications for allergy testing in children, how to interpret IgE tests, and when results must be paired with the clinical history to be meaningful. The child eats incrementally increasing amounts of the food in a controlled medical setting while being observed for reactions. If no reaction occurs through the full dose, the allergy is not confirmed. If a reaction does occur, treatment is on hand immediately. OFCs are also used to confirm when a child has outgrown an allergy. They are not done at home.

Needless elimination diets based on test results alone, without a confirmed clinical allergy, can cause nutritional deficits in growing children and should be avoided 3Ref 3American Academy of Pediatrics (2024).Food Allergies in Children: Causes, Symptoms, Diagnosis & Treatment.Risks of unnecessary elimination diets in children without confirmed allergy and the importance of allergist-coordinated diagnosis.

Patch testing for contact and eczema triggers

Patch testing is different from skin-prick testing and is used to identify contact allergens — substances that cause a delayed skin reaction (allergic contact dermatitis) when they touch the skin, such as nickel, certain preservatives, or fragrance components. Patches containing small amounts of test substances are applied to the back, left in place for 48 hours, and then read 48–96 hours after removal. It is not useful for food allergy or environmental allergy; it targets the type of immune reaction responsible for contact eczema. A pediatric dermatologist or allergist performs this test and interprets results in the context of the child's skin history 2Ref 2Boyce JA, Assa'ad A, Burks AW, et al.; NIAID-Sponsored Expert Panel (2011).Guidelines for the Diagnosis and Management of Food Allergy in the United States: Summary of the NIAID-Sponsored Expert Panel Report.Skin-prick test methodology, wheal size threshold for positive result, and patch testing for contact allergens.