What is it?
Food allergy is an adverse immune-mediated response that occurs reproducibly from the ingestion, inhalation, or skin contact with a specific food.
There are three types of food allergy: immunoglobulin E (IgE) mediated, non-IgE mediated, and mixed.1 Food allergy is primarily IgE mediated. Symptoms are immediate and can involve multi-organ systems. This article will focus on IgE-mediated reactions to foods. Allergy can develop to almost any food but common allergens include cow’s milk, eggs, and peanuts, and symptoms usually manifest in childhood.
When should food allergy be suspected?
The GP should consider a diagnosis of food allergy in an individual who repeatedly develops one or more of the following symptoms within minutes and up to 2 hours after exposure to a particular food:2
mucocutaneous — urticaria (wheals or hives), angioedema (swelling of the subcutaneous or submucosal tissue mainly affecting the lips, tongue, and eyelids), erythema, or pruritus;
gastrointestinal — abdominal pain or vomiting;
cardiorespiratory — respiratory distress, wheeze, stridor, hoarse voice, or syncope; and/or
anaphylaxis: severe, potentially life-threatening, multi-system, allergic reaction of rapid onset.
Why is it important for GPs to be knowledgeable about food allergy?
In the UK, up to one in 13 children and one in 50 adults are estimated to have a food allergy.3 Food allergy is increasing in prevalence globally and it can significantly affect the quality of life of patients.
Despite this increasing prevalence, knowledge on how to manage it needs significant improvement, as evidenced by only 33% of primary care clinicians expressing a self-perceived level of knowledge regarded as adequate.4
When should I consider testing in the community and specialist referral?
Food allergy testing should be targeted at patients with a suggestive history of rapid onset of symptoms (within 1–2 hours) after exposure to a food.5 This is because IgE blood tests are sensitive but not specific, and may identify sensitisation to the allergen (detectable circulating IgE) in many individuals who are not clinically allergic.6 Blanket screening is best avoided and only patients who have a moderate to high probability of a food allergy should be tested.
GPs should offer referral to a local allergy clinic if there is suspected food allergy and any of the following:5
previous episode with acute systemic symptoms such as respiratory distress, airway swelling, hypotension, or collapse (urgent referral);
poorly controlled asthma or a history of food allergy;
allergy testing is needed to confirm the diagnosis or if the diagnosis is uncertain;
strong parental concern of food allergy despite the lack of a supporting history;
clinical suspicion of multiple food allergies;
strong clinical suspicion of food allergy but allergy tests are negative; or
any patient who has been prescribed an adrenaline autoinjector (AAI) for suspected food allergy.
In selected cases, referral may also be offered for infants with severe eczema or those with a family history of severe food allergy even if they have never eaten the potentially offending allergen.
Cow’s milk protein allergy (CMPA) is common and is an immune-mediated reaction to cow’s milk proteins primarily seen in infancy and childhood, which tends to resolve with age. IgE-mediated CMPA presents with vomiting, urticaria, or anaphylaxis within 2 hours of exposure. Non-IgE-mediated CMPA causes delayed symptoms comprising crying, abdominal pain, vomiting, and diarrhoea occurring within 2 to 72 hours of exposure and can lead to a failure to thrive.
There is an overlap of symptoms in gastroesophageal reflux disease, lactose intolerance, and CMPA, but recurrent episodes of watery diarrhoea or the presence of blood or mucus in the stool after exposure to cow’s milk points towards CMPA. The complete resolution of symptoms upon starting a cow’s milk exclusion diet is also suggestive of CMPA but not definitive, and so referral for specialist review is recommended in order to avoid unnecessary dietary restrictions.
How can I treat food allergy in the community?
Anaphylaxis
Anaphylaxis is a life-threatening, systemic hypersensitivity reaction characterised by acute airway symptoms (pharyngeal or laryngeal oedema), bronchospasm, cardiovascular collapse, urticaria, and angioedema.7
A systemic allergic reaction that does not include life-threatening features – that is, affecting the airways or the cardiovascular system – is not anaphylaxis, and should be termed a generalised allergic reaction.
If anaphylaxis is suspected, the patient should be treated with intramuscular adrenaline and immediate ambulance transfer to the emergency department arranged. Patients should be referred for specialist out-patient review. In the interim, they should be prescribed two AAIs and receive training on its use.
Guideline for adrenaline autoinjector prescription in the community
If in doubt, AAIs should be prescribed but always alongside an urgent referral to the allergy service.5 Indications for prescription of an AAI are as follows:8,9
history of anaphylaxis — if the patient is at continuing risk from allergic reactions to identified triggers (confirmed allergen/s) or unidentified triggers (idiopathic anaphylaxis);
exercise-induced anaphylaxis or other co-factor-related food allergic reactions;
food allergy and coexisting unstable or moderate to severe, persistent asthma (most food allergy-related fatalities occur in those with unstable asthma); and
mild food allergy in high-risk patients (patients who react to trace exposure of the food or those with asthma).
AAIs are not normally recommended8 in the following clinical situations:
if known allergen can be avoided (for example, drug allergy);
family history of anaphylaxis alone (no personal history);
local reactions to insect stings; and
resolved food allergy in children — this should be established by a specialist (Box 1).
A focused allergy history is critical in determining whether there is a high probability of food allergy and if further investigation and referral are required. Testing should be targeted at patients with a clinical history suggestive of IgE-mediated allergy. The patient and/or their carer should be supported if they require further information on how to avoid particular allergens and on the use of AAIs by referring them to appropriate organisations.
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Box 1. Key guidelines for primary care
How can I treat mild food allergy in the community?
Management of food allergy if emergency admission or referral is not required.5 Mucocutaneous symptoms can be treated with non-sedating antihistamines such as loratadine. GPs should consider adding a short course of an oral corticosteroid only if cutaneous symptoms are severe.
If there is significant angio-oedema affecting the upper airway or rapid progression of symptoms, the GP should give intramuscular adrenaline and refer immediately to hospital.
Oral allergy syndrome (OAS) is when a person who is allergic to pollen later develops allergy symptoms upon exposure to raw vegetables, fruits, or nuts. It affects up to 50% of UK adults with hayfever. In patients with OAS, trigger foods can be eaten if cooked or processed and non-sedating antihistamines used for symptomatic relief.
The GP should ensure there is an individualised written food allergy management plan that includes allergen avoidance, thorough reading of labels, and avoidance of foods that are not labelled or lack allergen information. Asthma should be optimally managed. Any change in the allergy management plan should be communicated to schools. Most breastfeeding mothers do not need to avoid foods that their infants are allergic to.
Patients should be provided with sources of allergy information and support, such as the British Society of Allergy & Clinical Immunology (BSACI) Allergy Resource for Doctors & Patients (https://www.bsaci.org/resources/patient-information-leaflets-2/).
Notes
Provenance
Freely submitted; externally peer reviewed.
Competing interests
Siraj Misbah was a member of the Medicines and Healthcare products Regulatory Agency Expert Working Group on Adrenaline Autoinjectors.
Contributors
Saud Jukaku was the lead author of the manuscript. Vincent Crump provided an expert allergy perspective and critically revised the manuscript. Siraj Misbah critically edited the manuscript and provided advice on the bibliography and relevant guidelines.
- © British Journal of General Practice 2025