Rash, swelling or itching after eating certain types of foods may not signal a food allergy. Certain types of foods naturally contain high levels of histamine, a chemical that triggers the symptoms of an allergic reaction. Most people can eat these foods without experiencing symptoms whereas others are more sensitive to the effects of histamine. People who are especially sensitive to histamines in foods can follow a histamine intolerance diet to minimize their exposure.
Histamines
Certain cells release histamines as a response to an allergen. Histamines trigger the typical allergic reaction of sneezing, itching, nasal congestion, mucus secretions and swelling. Histamines occur naturally in some types of foods, notes the website AllergyUK. Most people eat these foods without experiencing allergic symptoms because an enzyme called diamine oxidase breaks down the histamines ingested in foods. Some people, however, have too little diamine oxidase. Their bodies are unable to break down the histamines in foods and they experience allergic symptoms such as headache, rash, swelling, itching, abdominal pain, diarrhea, nausea and vomiting.
Histamine Intolerance
In most cases of histamine intolerance, individuals lack sufficient quantities of diamine oxidase, according to researchers Laura Maintz and Natalija Novak in an article published in the November 2010 issue of "The American Journal of Clinical Nutrition." In other cases, certain foods or medications may inhibit the action of diamine oxidase or stimulate cells to release histamine. With the enzyme blocked or at insufficient levels, the histamine in foods can trigger allergy-like symptoms.
Intolerance vs. Allergy
Histamine intolerance may be confused with true food allergy because the symptoms are virtually identical, explain Maintz and Novak. Allergy challenge tests will be negative, however. With a true food allergy, small amounts of the food trigger symptoms. In histamine intolerance, the effect is cumulative and a single food may not cause symptoms. Also, histamine levels in foods vary and the reaction is influenced by the amount of the food eaten, storage of the food, alcohol consumption, and the presence of other proteins.
Histamine Intolerance Diet
A histamine intolerance diet seeks to reduce the amount of foods high in histamine and those that trigger histamine release from cells, explains AllergyUK. The diet begins by avoiding high-histamine foods for two weeks, then you gradually introduce foods back into your diet until you reach a tolerance level. If your symptoms do not improve while you are following the low histamine diet, something else is causing your symptoms and you can add all the foods back into your diet. Histamine in foods is unaffected by cooking or freezing, advises the website Histame. Improperly stored food, however, begins to spoil, which causes histamine to form.
High Histamine Foods
When following a low histamine diet, avoid seafood, eggs, poultry, aged cheeses, yogurt and processed or smoked meats, recommends AllergyUK. Also eliminate spinach and tomatoes -- including ketchup and sauce -- and most fruits, including citrus fruits, berries and raisins, with the exception of apples and pears. Additives such as artificial preservatives and colorings are prohibited, as are herbs and spices such as cinnamon, chili and curry powders, cloves, anise, nutmeg and cayenne. Do not use any fermented products, such as soy sauce, herbal or regular tea, chocolate, sauerkraut, pickles, alcohol, vinegars, licorice or cola. Permitted foods include fresh meats other than chicken, root vegetables, peas, beans and grains such as rice, wheat, oats and corn.
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