Allergy Testing for Infants: What Parents Need to Know

When your baby develops symptoms that suggest an allergy, the question of testing often arises. Many parents are surprised to learn that even very young infants can be safely and effectively tested for allergies. At LACK Clinic, we regularly assess babies in their first months of life to identify allergic triggers and develop appropriate management strategies.

Can babies under 6 months be tested for allergies?

Yes, absolutely. There is no lower age limit for allergy testing. Food allergies in particular can manifest very early in life, sometimes within days or weeks of birth. Early identification of allergic triggers can be crucial for managing symptoms and potentially influencing the course of allergic development.

Our experience at the LACK Clinic, supported by research including Professor Lack's groundbreaking studies, confirms that allergy testing in young infants is both safe and valuable when performed by specialists with paediatric expertise.

Why early testing matters

Identifying the cause of symptoms

Babies cannot tell us what's bothering them, making diagnosis challenging. Common symptoms that might indicate allergies in young infants include:

• Eczema or other skin rashes
• Persistent crying or fussiness, especially after feeds
• Feeding difficulties or reluctance to feed
• Vomiting or reflux symptoms
• Abnormal stool patterns (constipation or diarrhoea)
• Poor weight gain
• Sleep disturbances

When these symptoms are present, allergy testing can help determine whether an allergic reaction is the underlying cause.

Preventing the allergic march

Research increasingly suggests that early identification and management of allergies may help prevent what allergists call the "allergic march" – the progression from eczema to food allergies to respiratory allergies like asthma and hay fever.

Early intervention, particularly for infants with eczema, may reduce the risk of developing additional allergic conditions as they grow.

Guiding feeding decisions

For breastfeeding mothers, identifying specific food allergies in their infant can help guide maternal dietary adjustments that might improve the baby's symptoms.

For formula-fed babies, testing can determine whether a specialised formula might be beneficial.

As solid foods are introduced, testing results can inform safe feeding practices and appropriate introduction of allergenic foods.

Types of allergy testing for babies

Several testing methods are available for young infants, each with specific benefits in different situations.

Skin prick testing

Skin prick testing (SPT) is the most common form of allergy testing and can be performed on infants of any age. During this procedure:

• A small drop of allergen extract is placed on the skin (usually the back in very young infants)
• The skin is gently pricked through the drop using a sterile lancet
• After 15 minutes, the skin is examined for a reaction (a small raised bump similar to a mosquito bite)

This procedure:

• Is quick (typically 20-30 minutes for the entire process)
• Provides immediate results
• Is minimally invasive
• Causes only momentary discomfort

For babies, we typically limit the number of tests performed at one time based on the infant's size and skin area available.

Blood testing

Blood tests measuring specific IgE antibodies are an alternative or complement to skin testing. These tests:

• Require just a single blood draw
• Allow testing for multiple allergens from one sample
• Are particularly useful when skin conditions like widespread eczema make skin testing difficult
• Can be performed regardless of medications the baby might be taking

While blood tests have historically been considered slightly less sensitive than skin prick tests for some allergens, advances in laboratory techniques have significantly improved their accuracy.

Food challenges

In certain situations, especially when test results are unclear or there is a discrepancy between test results and the baby's history, a supervised food challenge may be recommended. This involves:

• Giving the baby small, gradually increasing amounts of the suspected food allergen
• Careful monitoring for any reactions
• Medical supervision throughout the process

Food challenges are generally reserved for situations where the risk of a reaction is low based on previous testing or history.

Limitations of allergy testing in infants

While testing can provide valuable information, parents should be aware of certain limitations:

Number of tests possible

Very young babies have limited skin surface area, which restricts the number of skin tests that can be performed in a single session. Your allergist will prioritise testing based on your baby’s history and likely triggers.

Interpreting results

Both skin prick tests and blood tests can sometimes yield “false positives” – showing sensitivity to foods that don’t actually cause symptoms when eaten. This is why test results are always interpreted alongside the baby’s clinical history.

Future development

A negative test in early infancy doesn’t guarantee a child won’t develop allergies later. Some allergies emerge as children grow and are exposed to new environments and foods.