In the UK, 14 allergens must be declared whenever they appear as ingredients in food — whether on product packaging, restaurant menus, or catering provision. These are the substances responsible for the most serious and most common allergic reactions in the UK population, ranging from mild oral allergy syndrome to fatal anaphylaxis. Understanding each allergen, where it hides beyond its obvious sources, and what the law requires businesses to tell you is essential knowledge for anyone managing food allergies or responsible for feeding people with them.
This guide covers all 14 allergens in practical detail — not just what they are but where they appear unexpectedly, what cross-reactivity means for each, and what UK law requires at the point of sale.
1. Cereals Containing Gluten
This covers wheat, rye, barley, oats, and their hybridised varieties (spelt, kamut, triticale). For people with coeliac disease, any amount of gluten triggers intestinal immune damage. For those with non-coeliac gluten sensitivity, symptoms are real but the immune mechanism differs. For wheat allergy specifically (separate from coeliac), IgE-mediated reactions to wheat proteins can cause urticaria, angio-oedema, and anaphylaxis.
Hidden sources beyond the obvious (bread, pasta, cereal): soy sauce (contains wheat unless specifically labelled gluten-free), malt vinegar (barley-derived), most beer and ale, many spice blends and seasonings, stock cubes and gravy granules, some medications and supplements. Cross-contamination in shared bakery environments and chip fryers is a significant practical risk for coeliac disease management.
2. Crustaceans
Prawns, crabs, lobster, langoustines, crayfish, and barnacles. The primary allergen is tropomyosin, a muscle protein that is heat-stable — cooking does not reduce allergenicity. Cross-reactivity within crustaceans is high, meaning allergy to one species reliably predicts allergy to others. Reactions to crustaceans are frequently severe; crustacean allergy is one of the more common causes of adult-onset anaphylaxis.
Hidden sources: prawn crackers, Thai curry pastes (often contain dried shrimp), fish sauces, some Asian dipping sauces, bisques and seafood soups where shrimp stock is used. Cross-contamination risk is high in fish and chip shops and restaurants where crustaceans are cooked alongside other food.
3. Eggs
Eggs in all forms — fresh, dried, powdered, and as derivatives (lysozyme, albumin, globulin, livetin). Egg allergy is one of the most common food allergies in children and often (though not always) outgrown by school age. In adults, egg allergy tends to persist.
Hidden sources beyond obvious uses in cooking: most baked goods, pasta (fresh pasta almost universally), mayonnaise and most creamy dressings, hollandaise sauce, many processed meats (as a binder), meringue, some wines and beers (egg white used as a fining agent). Lectins and other egg components are used in some vaccines — egg-allergic individuals need to notify vaccination providers.
4. Fish
All bony fish species — cod, haddock, salmon, tuna, mackerel, trout, bass, and hundreds of others. Fish allergy is separate from shellfish allergy (most people allergic to one are not allergic to the other, though individual testing is required). The primary fish allergen, parvalbumin, is heat-stable and can become airborne during cooking — proximity to fish cooking in a restaurant kitchen can trigger reactions in severely allergic individuals without any direct ingestion.
Hidden sources: Worcestershire sauce (contains anchovy), some Caesar dressings (anchovy), Thai and Vietnamese fish sauces used as base flavouring in curries and stir-fries, some pizza toppings, gelatine (if from fish sources), some omega-3 supplements.
5. Peanuts
Technically a legume, not a tree nut, but one of the most potent food allergens. Peanut allergy is the most common cause of fatal food-induced anaphylaxis in the UK. Reactions can be triggered by trace amounts — microgram quantities in highly sensitised individuals. Unlike many childhood food allergies, peanut allergy persists into adulthood in approximately 80% of cases.
Hidden sources: many Asian dishes (satay, pad thai, many Indonesian and Chinese preparations use peanuts extensively), West African cuisines, some chocolates and confectionery, groundnut oil (cold-pressed groundnut oil retains allergenic protein; highly refined groundnut oil usually does not, but caution is advisable). "May contain peanuts" warnings on packaging reflect real cross-contamination risk in shared manufacturing facilities.
6. Soybeans
Soya in all forms — whole soya beans, soya milk, tofu, tempeh, miso, edamame, and soya derivatives including soya lecithin, soya protein isolate, and soya flour. Soya is used extremely widely as a food additive in processed products, often in forms not obviously signalled by the product name.
Hidden sources: most protein bars and meal replacement products, many margarines and plant-based spreads, most processed bread (soya flour used as a protein and flour improver), many breakfast cereals, most meat alternatives and plant-based products, many chocolate and confectionery products.
7. Milk
All mammalian milks and products derived from them — butter, cream, cheese, yoghurt, ghee, casein, whey, and lactose. Milk allergy (IgE-mediated immune reaction to milk proteins, primarily casein and whey) is distinct from lactose intolerance (a digestive enzyme deficiency producing gastrointestinal symptoms without immune involvement). Milk allergy requires avoidance of all dairy; lactose intolerance may tolerate aged cheeses and lactase enzyme supplements.
Hidden sources: many canned tuna products (some contain casein), some crisps (butter flavouring), many processed meats, margarine and "non-dairy" creamers (may contain milk derivatives), some medications (lactose as an excipient).
8. Tree Nuts
Eight species are covered: almonds, hazelnuts, walnuts, cashews, pecan nuts, Brazil nuts, pistachio nuts, and macadamia nuts. Each is a distinct allergen — allergy to one tree nut does not necessarily indicate allergy to others, though cross-reactivity within botanical families is common (cashews and pistachios are related; walnuts and pecans are related). Individual allergen testing identifies which specific species a person reacts to.
Hidden sources: marzipan and frangipane in pastries, praline in chocolates and desserts, pesto (pine nuts — technically not a tree nut under UK law but relevant), many baked goods and granolas, flavoured coffees, liqueurs (Amaretto, Frangelico), many Asian dishes. At Vanda's Kitchen, tree nuts are structurally absent from our kitchen — not present rather than kept separate, providing genuine safety rather than procedural assurance.
9-14: The Remaining Six Allergens
Celery (including celeriac, celery seed, and celery as a vegetable): found in many stocks, soups, spice blends, and some meat products. Celery allergen survives cooking. Mustard (seeds, powder, prepared mustard, mustard oil): appears in many sauces, dressings, processed meats, and Indian cuisine. Sesame (seeds and oil): increasingly common in health foods, bread toppings, tahini, hummus, and Asian sauces. Sesame allergy rates have increased significantly in recent years. Sulphur dioxide and sulphites (above 10mg/kg or 10mg/litre): preservatives in dried fruit, wine, beer, processed meats, pickled products, and many processed foods. Lupin: a legume increasingly used in gluten-free and high-protein products; cross-reacts with peanuts in 20-40% of peanut-allergic individuals. Molluscs (oysters, mussels, clams, scallops, squid, octopus): distinct from crustaceans; reactions can be severe.
What UK Law Requires
Under Natasha's Law (October 2021), all pre-packed for direct sale (PPDS) food must display a full ingredients list with allergens emphasised — bold, italics, or different colour. Food sold loose requires allergen information to be available on request at minimum; many businesses now provide full written allergen information proactively. Vanda's Kitchen provides full allergen information for all products as a standard practice — our completely nut-free kitchen means tree nuts and peanuts carry no cross-contamination risk regardless of other ingredients.