Nearly a third of people living in the U.S. believe they have a food allergy, according to a recent study published in The Journal of the American Medical Association. But only 8% of children and less than 5% of adults have true food allergies. Experts say food allergies are definitely being over-diagnosed or in many cases erroneously self diagnosed. It's because people don't understand what really constitutes a food allergy and they often misuse the term.

You can't eat cheese, feel sick, and claim you have a food allergy, but then turn around and enjoy ice cream and feel OK. With a true food allergy, the trigger - milk protein in this case - does not change and the trigger will always set off the same immune system response.

A food allergy is a very specific immune system response involving either an immunoglobulin antibody IgE or T-cells. Both are immune system cells that react to a particular food protein, like milk protein. An IgE reaction occurs within minutes to an hour or so of either smelling, touching, or ingesting a particular food. The presence of the food triggers the immune system to over-react and interpret the food as harmful. Histamine is released, causing symptoms that range from mild to severe, including hives, itching, trouble breathing, wheezing, and anaphylaxis. Allergic reactions to food can be serious. About 30,000 Americans per year go to the emergency room due to catastrophic allergic reactions to food, and as many as 200 die every year from food allergies, according to the Food Allergy and Anaphylaxis Network.

Food intolerance is often confused as food allergy.

Food intolerance occurs when the body lacks a particular enzyme to digest that food. Two common examples are lactose intolerance and celiac disease, an autoimmune disorder in which the gastrointestinal tract cannot process gluten, a protein in wheat-based products such as cereal and bread. An intolerant person avoids the foods that trigger a reaction, but these reactions aren't caused by the immune system and they are not life threatening.

Most people who claim food allergies really have food sensitivity.

People with food sensitivity generally have an unpleasant reaction to certain foods - perhaps they develop acid reflux, nausea, or abdominal cramps - but these are not immune system reactions, and these reactions do not always occur in the same way when eating the food.

I think I have a food allergy, so I'll just avoid the offending food.

If you suspect you have a food allergy, just skipping the food that irritates you isn't enough. Unintentional food exposures occur, even in the most cautious individuals with true food allergy. The self-diagnosed individual is unlikely to be properly prepared to manage this potentially life-threatening reaction, such as use of an Epi-Pen." Epi-pen and Twinject are injectable forms of epinephrine.

Proper diagnosis of food allergy is essential.

Blood tests can also help diagnose a true food allergy by measuring IgE levels and determine whether there's a true food allergy. But blood tests can produce false-positives -- results that indicate an allergy when there isn't one -- in patients who have eczema, asthma, or other types of allergies because those people already have higher-than-average IgE levels. One accurate way to find out if you have a true food allergy is to visit your doctor and undergo a food challenge. The food challenge is managed by the doctor and done in a controlled environment at the doctor's office. It involves gradually giving higher doses of a particular food to see how much of that food is needed to trigger an immune system response. Another type of test -- the skin prick test -- can also indicate if the patient has a real food allergy by injecting a small amount of the allergen into the skin and checking whether the skin develops a bump or a rash.