Diagnosis and assessment of food allergy in children and young people in primary care and community settings: NICE clinical guideline

Allergy-focused clinical history

If food allergy is suspected — either by a healthcare professional or the parent or carer or child/young person — an allergy-focused clinical history should be obtained. The suggested process for this is outlined in Box 1.

Examination

An examination of the child or young person should pay particular attention to growth and physical signs of malnutrition, as well as any signs indicating allergy-related comorbidities, such as atopic eczema, asthma, and allergic rhinitis.

Investigation and diagnosis

The history should help determine whether the mechanism is likely to be IgE mediated or non-IgE mediated. If the history is suggestive of IgE mediated reactions, the child or young person should be offered a skin-prick test and/or blood tests for specific IgE antibodies to the suspected foods and likely co-allergens. Atopy patch testing should not be used. Oral food challenges may also be necessary to aid the diagnosis. These should not be performed in primary care if an IgE-mediated reaction is likely.

The choice for testing is between skin-prick testing and specific IgE testing. The tests are considered similar in their diagnostic performance so choice of test will depend on what is available to the clinician and acceptable to the child/young person. The tests requested should be guided by the clinical history and the results interpreted by someone competent to do so. Skin-prick testing should only be performed by those who are competent in the procedure and in locations where an anaphylactic reaction can be managed. Facilities available for routine childhood vaccinations are felt to be appropriate.

If the history is suggestive of non-IgE mediated reactions, elimination and reintroduction of the suspected allergen is recommended. The suspected allergen should be eliminated from the diet and reintroduced after 2–6 weeks of elimination. A recurrence of symptoms on reintroduction is necessary to confirm the diagnosis. Children and young people with severe systemic reactions should have been referred to secondary care and the reintroduction of the suspected allergen may need to take place in that setting.

Information for parents and carers

Age-appropriate advice should be given on:

• type of allergy suspected;

• risk of severe allergic reaction;

• potential impact of the suspected allergy on other healthcare issues, including appropriateness of vaccination (note: allergy to egg is not a contraindication to having the measles, mumps, rubella vaccination but influenza and yellow-fever vaccinations contain egg protein);

• diagnostic process, that may include an elimination diet followed by a possible planned re-challenge or initial food reintroduction procedure;

• skin-prick tests and specific IgE antibody testing, including the safety and limitations of these tests; and

• referral to secondary or specialist care.

If a food elimination diet is advised as part of the diagnostic process, the child/young person and their carer should be offered information on how to implement that diet. Information given must take into account socioeconomic status as well as cultural and religious issues, and should include:

• what foods and drinks to avoid;

• how to interpret food labels;

• alternative sources of nutrition to ensure adequate nutritional intake;

• the safety and limitations of an elimination diet; and

• the proposed duration of the elimination diet.

For babies and young children with suspected allergy to cow's milk protein, offer:

• mothers who are breastfeeding advice on food avoidance;

• mothers of formula-fed babies information on the most appropriate hypoallergenic formula or milk substitute (advice from a dietitian is advised); and

• the child/young person, or their parent or carer, information about the support available, and details of how to contact support groups.

GPs should note that an allergy to cow's milk protein should still be considered if the infant fails to respond to extensively hydrolysed formulas as, sometimes, amino acid formulas are necessary to eliminate the allergen sufficiently not to cause symptoms.

Referral to secondary care

Referral to secondary care is suggested if the child/young person has:

• an acute systemic reaction;

• a severe delayed reaction;

• faltering growth in combination with one or more of the gastrointestinal symptoms;

• significant atopic eczema, where multiple or cross-reactive food allergies are suspected by the parent or carer;

Referral is also suggested if there is:

• persisting parental suspicion of food allergy (especially in children/young people with difficult or perplexing symptoms), despite a lack of supporting history; or

• clinical suspicion of multiple food allergies.

After initial investigations, the following individuals should also be referred:

• those who have not responded to a single-allergen elimination diet;

• those with asthma who have confirmed IgE mediated food allergy (children with asthma are more at risk of severe reactions); and

• those in whom there is a strong clinical suspicion of IgE mediated food allergy but allergy test results are negative.

Alternative testing

There is no role for vega testing, applied kinesiology, hair analysis, and serum-specific immunoglobulin G testing in the diagnosis of food allergy in children and young people.