From the Guidelines
Allergy blood tests should be considered in children as young as 4-6 months of age, especially those with severe eczema, egg allergy, or both, as early introduction of peanuts can help prevent peanut allergy. This is based on the most recent guidelines from the NIAID, which recommend introducing foods containing peanuts early to infants to prevent peanut allergy 1. The introduction of peanuts should be done after measuring peanut-specific immunoglobulin E (IgE) or performing a skin prick test.
When diagnosing an allergy via peanut-specific IgE, a level less than 0.35 kUA per L has a strong negative predictive value, making this test beneficial in certain situations, such as family medicine and pediatric offices, to avoid unneeded subspecialist referral or to shorten the delay in introducing peanuts into the patient's diet 1.
In general, blood tests for allergies can be performed at any age, but they are most reliable in children over 2 years old. Before age 2, the immune system is still developing, which can lead to less accurate results and potential false positives. For infants and very young children with suspected allergies, doctors typically rely on clinical history, physical examination, and elimination diets before recommending blood tests.
Some key points to consider when deciding on the timing of allergy testing include:
- The child's specific symptoms and medical history
- The presence of severe eczema, egg allergy, or both
- The potential benefits of early introduction of peanuts in preventing peanut allergy
- The need for careful interpretation of blood test results, especially in young children
It's essential to note that the quality of evidence for the appropriate age to test for response to foods known to commonly cause IgE-mediated food allergy in infants or young children with atopic dermatitis (AD) or other risk factors is low, and the contribution of expert opinion is significant 1. However, the most recent guidelines from the NIAID provide a clear recommendation for the introduction of peanuts in infants with severe eczema, egg allergy, or both, which can help guide the decision on when to perform allergy blood tests 1.
From the Research
Allergy Blood Test Age
There is no specific age recommended for performing an allergy blood test. However, the decision to undergo an allergy blood test should be based on the presence of symptoms suggestive of an allergy, regardless of age 2.
Factors Influencing Allergy Testing
The following factors can influence the decision to perform an allergy blood test:
- Presence of persisting or recurrent symptoms suggestive of an allergy 2
- Severity of symptoms 2
- Family history of allergies 3
- Presence of other allergic diseases, such as asthma or atopic dermatitis 4
Age-Related Considerations
While there is no specific age recommendation for allergy blood testing, it is noted that:
- Infants are more likely to have allergies to cow's milk 3
- Peanut allergy is more commonly diagnosed in older children 5
- Some childhood allergies can be outgrown by adulthood 3
- Adults can also develop new IgE-mediated food allergies 3
Diagnostic Methods
Allergy blood tests, such as allergen-specific IgE tests, can be used to confirm an allergic trigger suspected on the basis of history 4. However, a positive test result does not always equate with clinical allergy 4. Other diagnostic methods, such as skin prick tests and oral provocation tests, may also be used to diagnose allergies 3, 6.