Many parents wonder whether their baby can be allergy tested — and if so, when and how. The short answer is yes: allergy testing can be performed in babies from the first weeks of life. However, the interpretation of results in infants requires specialist expertise, as the immune system is still developing and results must always be interpreted in the context of the clinical history.

This article explains when allergy testing is appropriate in babies and infants, what tests are used, and what the results mean.

When Should a Baby Be Referred for Allergy Testing?

Allergy testing in infants is most useful when there is a clear clinical history suggesting allergy. Common reasons for referral include:

  • Immediate reactions to food: Hives, vomiting, swelling or wheeze within minutes to 2 hours of eating a specific food
  • Suspected cow's milk allergy:Eczema, reflux, vomiting, diarrhoea, blood in stools or faltering growth in a formula-fed or breastfed baby
  • Severe or early-onset eczema:Eczema presenting in the first few months of life, particularly if severe or not responding to standard treatment
  • Family history of severe allergy: A sibling with peanut allergy or anaphylaxis, particularly if the baby also has eczema
  • Before introducing high-risk foods: Babies with severe eczema or existing food allergy may benefit from allergy testing before introducing peanut or other high-risk foods

What Allergy Tests Are Used in Babies?

Skin Prick Testing (SPT)

Skin prick testing can be performed in babies from birth. A small drop of allergen extract is placed on the forearm and a lancet is used to make a tiny prick through the drop. If the baby is sensitised to that allergen, a small raised wheal (like a nettle sting) develops within 15–20 minutes.

SPT is quick, safe and well tolerated in babies. The lancet causes minimal discomfort — less than a blood test. Results are available immediately at the appointment. Dr Anandarajan uses age-appropriate reference ranges to interpret results in infants.

Specific IgE Blood Tests

Specific IgE blood tests (also called RAST or ImmunoCAP tests) measure the level of allergen-specific IgE antibodies in the blood. They can be performed at any age and are particularly useful when skin prick testing is not possible (e.g. due to severe eczema on the arms, or if the baby cannot stop antihistamines).

A small blood sample is taken — usually from a vein in the arm or hand. Results are typically available within a few days. Dr Anandarajan will interpret the results in the context of the clinical history.

Component-Resolved Diagnostics (CRD)

Component-resolved diagnostics test for specific proteins within an allergen. For example, in peanut allergy, testing for Ara h 2 (a storage protein) is a better predictor of severe reactions than total peanut IgE. CRD is available at Belfast Children's Allergy Clinic and can be particularly useful in infants with eczema and suspected peanut sensitisation.

What Do Allergy Test Results Mean in Babies?

A positive allergy test result means the baby is sensitised to that allergen — their immune system has produced IgE antibodies against it. However, sensitisation does not always mean clinical allergy. Many babies are sensitised to foods they can eat without any symptoms.

Conversely, a negative allergy test does not always rule out allergy — particularly for non-IgE-mediated reactions (delayed reactions), which do not involve IgE antibodies and will not be detected by skin prick testing or specific IgE blood tests.

This is why allergy test results must always be interpreted by a specialist in the context of the full clinical history. Dr Anandarajan will explain what the results mean for your baby and provide a clear management plan.

What Happens at an Allergy Appointment for a Baby?

At the appointment, Dr Anandarajan will take a detailed history of your baby's symptoms, feeding history, family history of allergy, and any previous reactions. He will then recommend appropriate allergy tests and perform them at the appointment where possible. Skin prick test results are available within 15–20 minutes. Where specific IgE blood tests are required, results typically take 2–3 weeks, after which a full management plan is provided, including dietary advice, formula recommendations if appropriate, and guidance on introducing foods.

Read more about what happens during an allergy testing appointment.

Book an Appointment

Dr Anandarajan sees babies and children from birth to age 16 at Kingsbridge Private Hospital and Ulster Independent Clinic, Belfast. No GP referral is required. Call 028 9066 7878 or book online at kph.fyi/Book-MAnandarajan.