La guía completa de alergias alimentarias

Understanding Food Allergies

A food allergy is an immune system reaction that occurs after eating a specific food. Even a tiny amount of the allergenic food can trigger symptoms ranging from mild (hives, itching, tingling) to severe (anaphylaxis — a life-threatening reaction that can cause breathing difficulties, a dramatic drop in blood pressure, and loss of consciousness).

Food allergies affect an estimated 220 million people worldwide. In the United States alone, approximately 32 million people have food allergies, including 5.6 million children. The prevalence is increasing: childhood food allergies have risen by approximately 50% in the past two decades, though the exact reasons remain unclear.

It's important to distinguish between food allergies and food intolerances. A food allergy involves the immune system and can be life-threatening. A food intolerance (like lactose intolerance) involves the digestive system and, while uncomfortable, is generally not dangerous. Both require dietary management, but the level of strictness differs significantly.

The Major Food Allergens

Regulatory bodies around the world have identified the foods most commonly responsible for allergic reactions. These "major allergens" must be declared on food labels in most countries, though the specific list varies by region.

Milk (Dairy)

Milk allergy is the most common food allergy in infants and young children, affecting approximately 2-3% of infants. The allergenic proteins in milk are casein and whey. Milk proteins can hide under names including sodium caseinate, lactalbumin, lactoglobulin, and lactose (though lactose intolerance is a separate condition). Milk appears in bread, baked goods, processed meats, and many unexpected products.

Eggs

Egg allergy is the second most common childhood food allergy. The key allergenic proteins are ovalbumin, ovomucin, and ovotransferrin (primarily in the egg white). Eggs appear under names like albumin, globulin, lysozyme, and mayonnaise. They're used as binders, glazes, and clarifying agents in many food products and some wines.

Gluten / Wheat

Wheat allergy and Celiac disease (an autoimmune response to gluten) both require avoiding wheat, barley, and rye. Gluten hides in soy sauce, malt products, imitation seafood, gravies, and many sauces. Modified food starch can be wheat-derived. The complete Celiac guide covers this in depth.

Peanuts

Peanut allergy is one of the most common causes of food-related anaphylaxis. Peanuts are legumes (not true nuts) and can cause severe reactions from even trace exposure. They appear as peanut flour, arachis oil, groundnuts, and in many Asian sauces and baked goods.

Tree Nuts

Tree nut allergies cover almonds, cashews, walnuts, pecans, pistachios, macadamia nuts, hazelnuts, and Brazil nuts. Cross-reactivity between different tree nuts is common — many allergists recommend avoiding all tree nuts if you're allergic to one. Tree nuts appear in marzipan, pesto, nougat, and praline.

Soybeans

Soy is one of the hardest allergens to avoid due to its ubiquity in processed foods. Soy lecithin (E322) is used as an emulsifier in thousands of products. Soy appears as tofu, tempeh, miso, edamame, soy sauce, and textured vegetable protein.

Fish

Fish allergy typically involves finned fish (salmon, tuna, cod, etc.) and is often lifelong. Fish proteins appear in Worcestershire sauce, Caesar dressing, and Asian fish sauces. Omega-3 supplements and some fortified foods may contain fish oil.

Shellfish

Shellfish allergy covers crustaceans (shrimp, crab, lobster) and molluscs (clams, mussels, oysters, squid). It's the most common adult-onset food allergy. Glucosamine supplements are derived from shellfish shells.

Sesame

Sesame was added to the US major allergen list in 2023. It appears in hummus, tahini, many bread products, and Middle Eastern and Asian cuisines. Sesame oil is used in cosmetics and skincare.

Celery & Mustard

These are EU-mandated allergens but not part of the US Big 9. Celery salt and mustard powder appear in many spice blends, sauces, and processed meats. Travelers between regions should be aware of the differing labeling requirements.

Sulphites

Sulphites (E220-E228) are preservatives found in dried fruits, wine, beer, and many processed foods. They can trigger severe asthma attacks and other reactions in sensitive individuals.

Lupin

Lupin flour is increasingly used in gluten-free products. It's closely related to peanuts, with 35-50% cross-reactivity. It's a mandatory allergen in the EU but not in the US.

How to Stay Safe: Practical Strategies

1. Always read labels. Learn the complete label reading guide for your specific allergens.
2. Know the hidden names. Every allergen has multiple aliases. Our allergen database lists them all.
3. Understand cross-contamination. Read our cross-contamination guide for practical prevention strategies.
4. Use technology. The Alergio app scans barcodes and reads ingredient labels in 20+ languages, flagging allergens instantly.
5. Prepare for emergencies. Always carry your emergency medication (auto-injector) and wear a medical alert bracelet.
6. Communicate clearly. When eating out or traveling, use allergy cards to communicate your needs. Alergio's Travel Cards translate your allergies into multiple languages.

When to See a Doctor

If you suspect you have a food allergy, see an allergist for proper testing. Diagnosis typically involves skin prick tests, blood tests (specific IgE), and potentially oral food challenges. Self-diagnosis can be unreliable and may lead to unnecessary dietary restrictions — or, conversely, underestimate the severity of a real allergy.

Seek immediate emergency medical attention (call 911 or your local emergency number) if you experience symptoms of anaphylaxis: difficulty breathing, swelling of the throat or tongue, rapid pulse, dizziness, or a severe drop in blood pressure after eating.