The terms food intolerance and food allergies are often confused. Food allergies occur when the body has strong, immediate reactions to a food. The immune system is directly involved with a food allergy. With a food intolerance, though, the body has an unpleasant reaction to the food or additives.

Since not all reactions can be covered by the term food allergy, doctors use the term food intolerance to describe those unfavorable reactions that don't involve the immune response system. Allergy tests are used to detect allergens. Sometimes food intolerance is just the result of too much of the same thing over a long period.

Non-immune responses are also possible with some foods. You should be familiar with generic toxicity. This would be the body's reaction to known poisons such as arsenic, lead, and mercury. These poisons can occur naturally and show up in food when you least expect them to.

Naturally occurring substances can occur in such high concentrations that they make food unsafe to eat. Another category of food intolerance involves people who lack certain enzymes which are required to digest certain foods, such as lactose intolerance. These conditions are less dangerous but still serious.

Lactose intolerance is a familiar instance. There are those people whose bodies cannot digest milk because they lack the enzyme called lactose, which is needed to absorb the sugar lactose in milk. Most of us have levels high in this enzyme so we can tolerate milk and not have unpleasant side effects.

Another instance of food intolerance which is non-allergic in nature is the effect caused due to the presence of naturally seen chemicals present in food, or in additives which form a chemical reaction. The mentioned reactions are very like actual allergic reactions and there is a chance that they may get mistakenly tagged as food allergy.

There are various things which come under the food additives category. They include substances like preservatives, flavoring agents, coloring agents etc. Some familiar examples include tartrazine, MSG or monosodium glutamate, sulphur dioxide as well as benzoates. When chemical reactions are involved with respect to food or food additives, they are not actually allergic reactions since here the body's immune system is not involved.