Tree nut allergy is one of the most prevalent food allergies in UK adults and, unlike many childhood allergies, is outgrown in fewer than 10% of those affected — making it a lifelong management challenge for the vast majority. The eight tree nuts covered under UK allergen law are each botanically distinct allergens, which means the clinical picture varies considerably between individuals: some react to one specific species, others to several, and a smaller proportion to all eight. Understanding your specific allergy profile through proper testing is the foundation of both safe avoidance and unnecessary dietary restriction.
The Eight Covered Tree Nuts and Their Characteristics
Almonds are the most widely consumed tree nut in the UK and among the most prevalent in food products — appearing in marzipan, frangipane, amaretto, many pastries and cakes, almond milk, and almond flour used in gluten-free products. Almond allergy is one of the more common tree nut allergies in UK adults and can cause reactions across the full severity spectrum. People allergic to almonds may also react to other members of the Rosaceae family (peaches, apricots, cherries) through cross-reactivity with PR-10 proteins, though this pollen-food syndrome is milder than primary almond allergy.
Hazelnuts are notable for being the most common cause of oral allergy syndrome (OAS) in the UK — a mild, localised reaction (itching and swelling of the mouth and lips, clearing within minutes) caused by cross-reactivity with birch pollen proteins. OAS hazelnut reactions are common in adults and rarely progress to systemic anaphylaxis, but individuals with OAS still need to be aware of hidden hazelnut sources. Chocolate-hazelnut spreads, praline, Nutella and similar products, many chocolates, and coffee syrups are common hazelnut sources.
Cashews are botanically related to pistachios and mangoes (all in the Anacardiaceae family). Cross-reactivity between cashew and pistachio is high — the majority of cashew-allergic individuals also react to pistachios. Cashew allergy in children and adults can cause severe reactions and is among the more potent tree nut allergens. Cashews appear in many Asian dishes, some chocolates, and increasingly in dairy-free products where cashew cream is used as a milk substitute.
Walnuts and pecan nuts are related (both Juglandaceae family) and cross-react in a significant proportion of individuals. Walnut allergy can be severe; it appears in baked goods, salads, pesto and sauces, and many granola products. Brazil nuts are not closely related to other tree nuts and cross-reactivity is lower, but brazil nut allergy can be among the most severe of the tree nut allergies. Pistachio allergy is closely associated with cashew allergy. Macadamia nuts are less commonly consumed but appear in some chocolates, cookies, and luxury confectionery.
Cross-Reactivity Between Tree Nut Species
Cross-reactivity between tree nut species is common but not universal or predictable without testing. The general principles: nuts within the same botanical family cross-react more frequently (cashew-pistachio, walnut-pecan); nuts in different families can still cross-react through shared allergen proteins (particularly 2S albumins, which are present across many nut species and tend to produce more severe reactions). A person allergic to one tree nut cannot assume safety with other tree nut species without specific testing — but equally, they should not assume allergy to all eight without testing, as unnecessary avoidance of safe foods reduces nutritional variety and quality of life unnecessarily.
Specific IgE blood testing (available through NHS allergy clinics or private allergists) tests for sensitivity to individual nut species and provides the foundation for a personalised avoidance plan that avoids only the species that present actual risk. Component testing (for specific allergen proteins like Ara h 8 for OAS-type reactions vs Ara h 2 for systemic reactions) provides additional detail about reaction severity risk.
Hidden Sources: Where Tree Nuts Appear Unexpectedly
The obvious sources — mixed nuts, nut-containing chocolates, and clearly labelled nut products — are straightforward to avoid. The hidden sources require more vigilance:
Marzipan and frangipane: both almond-based and appear in a very wide range of pastries, cakes, Danish products, croissants, stollen (Christmas cake), and celebration cakes. Frangipane is used in tarts across many bakeries and patisseries.
Praline: a nut-based confection used extensively in chocolates, desserts, and pastry cream fillings. Any chocolate that describes a filling as "praline," "gianduja," or "nougat" is likely to contain hazelnuts or almonds.
Pesto: traditional Italian pesto contains pine nuts (technically not a tree nut under UK allergen law, but worth noting for those with multiple nut sensitivities). Some commercial pestos substitute cashews or walnuts for pine nuts — check labels carefully.
For nut-free catering across London, see our nut-free catering hub or order directly from our catering shop.
Nut oils: cold-pressed walnut oil, almond oil, and hazelnut oil retain allergenic protein and are relevant for people with those specific allergies. The same oils used in some skincare products are worth checking for people with severe nut allergies.
Asian cuisines: cashews appear in many Chinese and Indian dishes. Almonds in Mughlai cuisine. Thai satay may use nuts beyond peanuts in some preparations. Cross-contamination between nut species in restaurant kitchens where multiple nuts are handled is a consistent risk.
Dairy-free and vegan products: cashew cream is increasingly used in dairy-free cheeses, cream cheese alternatives, and vegan desserts. Almond milk and hazelnut milk are common dairy alternatives. These products may not have prominent nut labelling if the nut is considered the defining ingredient rather than an allergen addition.
Cereal bars, granola, and "healthy" snacks: mixed nuts, almond butter, and hazelnut spreads are extremely common in this product category, where the health positioning sometimes obscures allergen vigilance in labelling.
The Cross-Contamination Problem and Its Solutions
For individuals with severe tree nut allergies — particularly where the threshold dose for reactions is very low — "may contain tree nuts" warnings on packaging represent a real and meaningful risk. These warnings are voluntary and unstandardised, which means their presence on one product and absence on a similar product doesn't necessarily reflect different actual contamination risk — it may simply reflect different risk communication policies by the manufacturer. This creates a genuinely difficult practical challenge for severely allergic individuals who want to manage risk appropriately without eliminating an impractically large range of products.
The clearest structural solution is sourcing food from providers where nuts are entirely absent from the kitchen environment rather than managed through careful procedures. At Vanda's Kitchen near St Paul's, all eight tree nut species (and peanuts) are absent from our kitchen. No nut-containing ingredients enter our premises. This structural commitment eliminates cross-contamination risk at source — providing the genuine safety that severely tree nut-allergic individuals require rather than the procedural assurance that can fail under the pressures of a busy commercial kitchen.
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Related: Tree Nuts: The Complete UK List of What Is and Isn't a Tree Nut · Peanut Allergy: The Complete Guide to Symptoms, Hidden Sources, and Safe Eating in London