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Food allergies and food intolerances relate to the adverse reactions that occur in some people after consumption of certain foods. Allergies and intolerances are often mistaken for each other. Basically, a food allergy is where the immune system is upset after a particular food, whereas a food intolerance is where the digestive system is affected rather than the immune system. Compared with food intolerance, food allergy is less common but reaction is usually quicker and more severe. Other bad reactions to food are food toxicity and food aversion.

Food allergies

A food allergy occurs when tissue reacts abnormally to an antigen within the food, which can be a protein, something bound to it, or a food additive. The result is cell damage and histamine release, triggered by the antibody IgE. But the immune system is an amazing thing. Enzymes can change the constitution of food in the intestine, reducing the effect of the allergen. An antibody called IgA further reduces the allergen’s penetration. However, reaction can occasionally be severe and even life-threatening. An allergy can be caused by a very small amount of a food and can happen quite quickly. The protein or additive causing the reaction is actually harmless and has no adverse effect in most people.

Allergy rates are increasing worldwide. Babies and children are more prone to food allergies due to their naturally weaker immune systems. An estimated 6-8 percent of children currently suffer from food allergies compared with 2-4 percent of adults. Young children will often outgrow their allergies. However, allergies to foods such as nuts and fish are likely to remain.

Sometimes allergies run in families and can be hereditary. If a family member has an allergy, a child is 20-40 percent more likely to have an allergy. This increases to 50-80 percent if more than one member has an allergy. Breastfeeding helps strengthen a baby’s immune system and reduces the risk of allergies. Exposure to cigarettes, dust, mold, fur, and solid foods too early in an infant’s life all increase the risk.

Food intolerances

Food intolerance, on the other hand, can be the result of several things. A non-allergic histamine can be released after eating certain foods, such as shellfish or strawberries. The symptoms are often similar to a food allergy, with victims suffering headache, vomiting, facial swelling, urticaria around the body, and diarrhea. On many occasions, all that is required is anti-histamine tablets.

Then there are metabolic defects that can cause food intolerance. For example, people lacking the lactase enzyme will have trouble digesting milk or ice cream. Those intolerant to gluten in wheat can suffer celiac disease from eating bread. Another type of intolerance is where large quantities of certain food substances act like a drug in the body. An example is caffeine, which can cause palpitations and migraines. Various food additives such as colorings and flavorings can result in an intolerance in certain people. For example, sulfur dioxide affects about 40 percent of children with asthma.

Main foods causing allergies and intolerances

Main foods causing allergies include nuts, eggs, milk, sesame, fish and other seafood, grains such as wheat, and soy. Others are fruit, berries, potatoes, tomatoes, and cucumber.

Food allergy symptoms usually come on quicker than those of intolerance and can include an itchiness, burning or swelling of the mouth, tongue or lips, as well as a runny nose, rashes, urticaria, difficulty breathing, nausea, vomiting, cramps, diarrhea, and anaphylaxis where the airway can be blocked within minutes and the person can die of suffocation.

The causes of food intolerance are largely meat and dairy products, including milk, cheese, chocolate, eggs, fish, pork and chicken, but also food additives, flavor enhancers, strawberries, citrus fruit, tomatoes, and wine. Vegetarians tend to suffer less from food intolerance as they don’t eat dairy or meat.

Symptoms of food intolerance vary from person to person but some of the more common ones are headache, sweating, tremor, rapid breathing, nausea, vomiting, diarrhea, burning sensation, urticaria, face and chest tightness, and asthma. Longer term symptoms can include migraine, fatigue, anxiety and depression. Thus some symptoms are common to food allergies and food intolerances, sometimes making diagnosis more difficult.

Food toxicity

Neither food allergy nor food intolerance should be confused with food toxicity, where food is spoiled or becomes contaminated and the person suffers food poisoning from eating it. If you’re the only person to eat something and suffer, it’s hard to know if it’s food toxicity or another type of adverse reaction to food. However, if the whole family is sick or if a number of people at a party or restaurant are sick, then it’s probably food toxicity.

Food aversion

A fourth bad reaction to food is called food aversion, and is where a person convinces themselves that a particular food disagrees with them but tests find nothing. It is quite common.

There are several steps to take to avoid any of the four adverse reaction types to food. Determine what is causing the reaction by keeping a diary of food consumption and symptoms. Avoid the suspected foods one at a time. If you find the culprit, avoid it altogether. Check food labels to make sure it’s not in the products you buy. If you can’t isolate the problem, have skin prick and blood tests. Your doctor and dietician should be able to provide further advice.