A food allergy happens when the immune system mistakes a harmless food protein for a dangerous invader. This matters because even a tiny amount of the allergen can trigger symptoms in some people. Reactions can range from mild itching or hives to life-threatening anaphylaxis.
Understanding the science helps students see why allergies are medical conditions, not personal preferences.
Key Facts
- Food allergy is an immune reaction to a food protein, while food intolerance usually does not involve IgE antibodies.
- IgE antibodies can bind to allergens and attach to mast cells, preparing the body for a faster reaction next time.
- When an allergen cross-links IgE on mast cells, histamine and other chemicals are released.
- Histamine can cause hives, swelling, mucus production, vomiting, wheezing, and lowered blood pressure.
- The top 9 major food allergens are milk, egg, peanut, tree nuts, fish, shellfish, wheat, soy, and sesame.
- Epinephrine is the first-line treatment for anaphylaxis because it helps raise blood pressure, relax airway muscles, and reduce swelling.
Vocabulary
- Allergen
- An allergen is a substance, often a protein, that can trigger an allergic immune response.
- IgE antibody
- An IgE antibody is an immune protein that can recognize allergens and attach to mast cells and basophils.
- Mast cell
- A mast cell is an immune cell that releases histamine and other chemicals during allergic reactions.
- Histamine
- Histamine is a signaling chemical that causes many allergy symptoms, including itching, swelling, redness, and mucus production.
- Anaphylaxis
- Anaphylaxis is a severe, rapid allergic reaction that can affect breathing and blood pressure and requires emergency treatment.
Common Mistakes to Avoid
- Calling every bad reaction to food an allergy is wrong because many reactions are intolerances that do not involve IgE or mast cell activation.
- Assuming a small bite is always safe is wrong because highly sensitive people may react to tiny amounts or cross-contact with an allergen.
- Waiting to use epinephrine during anaphylaxis is wrong because delayed treatment can make a severe reaction harder to control.
- Thinking antihistamines replace epinephrine is wrong because antihistamines may reduce itching or hives but do not reliably fix airway swelling or low blood pressure.
Practice Questions
- 1 A cafeteria labels 36 packaged snacks. If 9 contain one of the top 9 allergens, what percent of the snacks contain a major allergen?
- 2 A student has a 0.30 mg epinephrine auto-injector. If a second dose is needed after 5 minutes and both doses are used, how many milligrams of epinephrine are given in total?
- 3 Explain why lactose intolerance can cause stomach symptoms after drinking milk but is not the same as an IgE-mediated milk allergy.