Peanut Allergy: The Complete Guide to Symptoms, Hidden Sources, and Safe Eating in London

Peanut allergy is the most common cause of fatal food-induced anaphylaxis in the UK, affecting approximately 2% of children and a significant proportion of adults. Unlike most childhood food allergies, peanut allergy persists into adulthood in around 80% of cases — making it a lifelong condition for the vast majority of those affected. The doses required to trigger severe reactions can be extraordinarily small in highly sensitised individuals, and the potential severity of reactions — including cardiac arrest — makes peanut allergy one of the most demanding allergen management challenges in everyday life.

This guide covers everything practically relevant: the biology of peanut allergy, the symptom spectrum, where peanuts hide beyond obvious sources, cross-reactivity and the tree nut question, emergency management, and how to navigate eating in London safely.

Why Peanut Allergy Is Particularly Serious

Several characteristics of peanut allergy combine to make it more dangerous than most other food allergies. Peanuts are legumes (related to soy, lentils, and chickpeas) but produce allergic responses that resemble tree nut allergies in their IgE-mediated mechanism and severity. The threshold dose for reactions in highly sensitised individuals is among the lowest of any food allergen — studies have documented allergic responses to as little as 1-2mg of peanut protein in some individuals. This makes cross-contamination from shared manufacturing equipment, cooking surfaces, and food service environments a genuine and serious risk.

Peanut allergy also exhibits a pattern of unpredictability that complicates management: a reaction that was mild or moderate in the past provides no guarantee about future reaction severity. The same individual can have mild skin reactions on some exposures and systemic anaphylaxis on others, influenced by factors including cofactors (exercise, alcohol, NSAIDs, and illness can all lower the reaction threshold), the form of the peanut (roasted peanuts are more allergenic than raw because roasting changes the allergen proteins), and stress. This unpredictability is why prescribed adrenaline auto-injectors must be carried at all times regardless of previous reaction history.

The Symptom Spectrum: Mild to Anaphylaxis

Peanut allergy symptoms typically begin within minutes to two hours of exposure, with the majority of serious reactions occurring within 30-60 minutes. The spectrum ranges from mild to life-threatening:

Mild to moderate symptoms: tingling or itching in the mouth and throat (oral allergy syndrome); skin reactions including urticaria (hives), eczema flare-up, or facial swelling particularly around the eyes and lips; nasal symptoms including congestion and sneezing; gastrointestinal symptoms including nausea, abdominal cramping, vomiting, or diarrhoea. These symptoms require antihistamines and close monitoring for progression.

Severe symptoms (anaphylaxis): significant throat and tongue swelling causing difficulty swallowing or breathing (stridor — a high-pitched breathing sound — is an emergency sign); bronchospasm causing wheeze and breathlessness; significant drop in blood pressure causing dizziness, faintness, or collapse; loss of consciousness. These are life-threatening and require immediate intramuscular adrenaline injection followed by emergency services. Anaphylaxis can progress from mild symptoms to life-threatening within minutes — the decision to use adrenaline should not be delayed waiting for symptoms to worsen.

Where Peanuts Hide: Beyond the Obvious

Peanut butter and salted peanuts are the obvious sources most people know to avoid. The hidden sources are where accidental exposures occur most frequently:

Asian cuisines: Thai, Indonesian, Malaysian, and Chinese cooking uses peanuts and peanut oil extensively, often in sauces and bases that don't explicitly signal peanut content in a dish name. Pad thai traditionally contains crushed peanuts. Satay is peanut-based. Many Chinese stir-fries use peanut oil. Vietnamese and Korean dishes frequently incorporate peanuts or peanut sauce. Cross-contamination risk in restaurant kitchens serving these cuisines is very high.

West African and Ghanaian cuisines: groundnut stew (maafe) uses peanuts as a core ingredient; many West African soups and sauces are peanut-based.

Chocolates and confectionery: many chocolates are produced in facilities that also process peanuts; some chocolate products include peanut butter or peanut paste. "May contain peanuts" warnings on chocolate are among the most common in UK food labelling.

Energy and protein bars: peanut butter is a common ingredient; many bars are produced in peanut-processing facilities.

Cold-pressed groundnut (peanut) oil: retains allergenic protein and can cause reactions. Highly refined peanut oil has the protein removed and is generally considered safe for most peanut-allergic individuals, but the distinction requires clear labelling — "groundnut oil" without specification is not safe.

Some cuisines' garnishes and toppings: peanuts as a topping are common enough in many Asian and fusion restaurants that the same serving tongs or surfaces used for peanut-topped dishes may contaminate other dishes. Always specify the allergy, not just the preference, to ensure staff understand the cross-contamination requirement.

Cross-Reactivity: Peanuts and Tree Nuts

For nut-free catering across London, see our nut-free catering hub or order directly from our catering shop.

Peanuts are legumes, botanically unrelated to tree nuts (almonds, cashews, walnuts etc), but cross-reactivity between peanut allergy and tree nut allergy is present in approximately 25-40% of peanut-allergic individuals. This cross-reactivity is not universal — many people with peanut allergy tolerate all tree nuts without reaction — but individual allergen testing (specific IgE testing for individual tree nut species) is essential to clarify the picture for each person. Blanket avoidance of all tree nuts based on peanut allergy alone, without testing, leads to unnecessary dietary restriction. Specific IgE testing through an NHS allergy clinic or private allergist identifies exactly which additional species, if any, require avoidance.

Lupin allergy also cross-reacts with peanut allergy in approximately 20-40% of peanut-allergic individuals. Lupin is increasingly used in gluten-free and high-protein products in the UK and is a declared allergen — checking labels for lupin flour, lupin seed, and lupin protein is important for peanut-allergic individuals.

Safe Eating in London

For peanut-allergic Londoners, several strategies reduce risk when eating out. Always disclose the allergy — not "I don't eat peanuts" but "I have a severe peanut allergy and need to understand the cross-contamination risk in your kitchen." Be specifically cautious with Asian cuisines, particularly Thai, Chinese, Indonesian, and West African, where peanuts are structurally embedded in the cooking and cross-contamination risk is high even when specific dishes don't contain peanuts. Choose restaurants or caterers where the kitchen doesn't routinely handle peanuts — structural absence is more reliable than careful procedures in a kitchen where peanuts are regularly present.

Vanda's Kitchen near St Paul's operates from a completely nut-free kitchen — peanuts and all tree nuts are absent from our kitchen environment entirely. This structural commitment means our food carries no peanut cross-contamination risk, providing the level of assurance that procedural accommodation in conventional kitchens cannot match.

Emergency Management

Anyone who has had a systemic allergic reaction to peanuts must carry two adrenaline auto-injectors (EpiPen or Jext) at all times — one is insufficient because reactions sometimes require a second dose, and the first may malfunction. Auto-injectors should be replaced before their expiry date. An emergency action plan — written, shared with family members, colleagues, and the school in children's cases — should specify when to administer adrenaline (use at first signs of systemic reaction; don't wait for severe symptoms), when to call 999, and what to do while waiting for emergency services. Annual review of the action plan and emergency medication with your GP or allergy team keeps it current and rehearsed.