Walnut allergy
Tree-nut allergy to walnuts.
About walnut allergy
Walnut is a true tree nut and a common cause of tree-nut allergy, which usually begins in childhood and is often lifelong. The reaction is IgE-mediated: the immune system produces antibodies to walnut storage proteins, and on later exposure these prompt mast cells to release histamine and other chemicals within minutes. Walnut is one of the more frequently implicated nuts in serious reactions and is a mandatory labelled allergen in the UK.
Symptoms usually develop rapidly and can range from an itchy mouth and hives to swelling, vomiting, wheeze and anaphylaxis with breathing difficulty or collapse. Because walnut and pecan share very similar proteins, people allergic to one are commonly allergic to the other, and there can be cross-reactivity with other tree nuts, so clinicians may advise caution across the group. Walnuts appear in baking, salads, sauces, cereals and confectionery, making hidden exposure a real concern.
Diagnosis uses skin-prick or specific-IgE blood tests, sometimes with component testing or a supervised challenge to define risk. Management relies on strict avoidance, careful label-reading and awareness of cross-contamination and "may contain" warnings. People at risk of severe reactions carry an adrenaline auto-injector and a written action plan. A severe reaction is a medical emergency: use the auto-injector without delay and call 999.
Common triggers
- Walnut and products containing it
Symptoms
- Itching or tingling in the mouth
- Hives, itching or eczema
- Swelling of the lips, face, tongue or throat
- Stomach cramps, nausea, vomiting or diarrhoea
- Wheezing or trouble breathing
- In severe cases, anaphylaxis
Avoidance & management
- Read ingredient labels every time
- Ask about ingredients and cross-contamination when eating out
- Keep the food out of shared cooking areas
- Carry prescribed antihistamines or an adrenaline auto-injector
- Seek emergency help for any severe reaction
Sources & references
Allergy safety: what everyone should know
Mild-to-moderate reaction signs
- Itching, hives or a raised rash
- Swelling of lips, face or eyes
- Tingling mouth, sneezing, runny nose
- Stomach pain, nausea or vomiting
Anaphylaxis — call 999 (UK) or 112 (EU) immediately
- Difficult or noisy breathing, wheeze, persistent cough
- Swelling of the tongue or tightness in the throat
- Dizziness, collapse, pale and floppy (young children)
- Use an adrenaline auto-injector (e.g. EpiPen) at once if prescribed, then call an ambulance even if symptoms improve
Allergy or intolerance? A true allergy involves the immune system and can escalate quickly; an intolerance (e.g. lactose intolerance) is unpleasant but not life-threatening. The symptoms overlap, so self-diagnosis is unreliable.
Getting tested: home-testing kits based on IgG are not diagnostically valid. If you suspect an allergy, ask a GP for referral to an allergy clinic for skin-prick or specific-IgE testing and a supervised food challenge where appropriate.