1. If you have a food allergy, blame your parents. It’s an inherited predisposition. In other words, if your family has a history of allergies, you are much more likely than, say, the child of allergy-free parents to develop a food allergy.
2. The development of a food allergy begins with one simple step: exposure to the food. If you never touch or eat a peanut, you’ll never develop a peanut allergy. Even that first peanut butter biscuit may be innocuous, but as you digest it, it triggers your immune system to produce IgE antibodies that will be activated the next time you eat the food.
3. It’s not the food that triggers the reaction but rather proteins within the food that are not broken down through cooking or by stomach acid or digestive enzymes. These proteins are absorbed through the gastrointestinal lining into your bloodstream then travel through your body.
4. The proteins interact with the IgE molecules on the surface of mast cells, triggering the cells to release inflammatory chemicals such as histamine. Where those chemicals are released determines your reaction. For instance, the mast cells on your skin are most likely to be affected by food allergies, leading to hives or atopic dermatitis (eczema), a skin condition characterized by itchy, scaly red skin. If mast cells in your ears, nose and throat are activated, your mouth may itch, and you may have trouble breathing or swallowing. If they are activated in your gastrointestinal tract, you may have abdominal pain, diarrhea or vomiting. If it happens in your lungs, you could have an asthma attack.
5. A food reaction can vary from mild tingling in the mouth to full-blown anaphylaxis with collapse. The reaction can start almost instantly as the food touches your mouth, or may develop more slowly over the next hour or so. This sequence is known as IgE-mediated food allergy, for the obvious reason that IgE antibodies are integral to the reaction.
6. You can also have a non-IgE-mediated food reaction. This occurs when a food triggers the production of T cells, which in turn call in other substances that activate your immune response, including inflammation. Most non-IgE-mediated food reactions result in gastrointestinal symptoms, such as gas, and are not life-threatening.
7. A combination of IgE-mediated allergy and non-IgE-mediated food sensitivity is also possible. For instance, you could have an allergy to milk and at the same time be lactose intolerant, meaning that you lack the enzyme that enables you to digest the milk sugar lactose.
8. If you are allergic to one food, you are more likely to be allergic to others. For instance, if you have a history of allergic reactions to prawns, you’re likely to be allergic to crab, lobster, and crayfish as well. Doctors call this cross-reactivity. Furthermore, people who have a birch-pollen allergy may also react to hazelnuts, apples, carrots, and celery. And if you’re allergic to latex, you should watch out for bananas.
9. Some people suffer from exercise-induced food allergy. In this form of allergy, if you eat a certain food and then exercise soon afterwards a reaction is triggered. You’ll find that as you work out and your body temperature rises, you begin to itch, become light-headed and soon have allergy symptoms such as hives or even anaphylaxis. The cure is simple: don’t eat for a couple of hours before exercising.
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