Drinking milk may upset your stomach, give you stomach cramps, bloating and all sorts of other unpleasant abdominal sequelae. But is your reaction to milk a food allergy or an example of food intolerance? And how do you know the difference?

Allergic reactions are responses to the antibodies your immune system produces when it identifies a protein as dangerous. Typically, allergic reactions involve the skin, the respiratory system and, less often, the digestive system: You may develop itchy skin, a rash or hives; you may also experience shortness of breath as your airway swells. Some people may also experience nausea, stomach pain and diarrhea as part of an allergic reaction. Allergic reactions can be mild or severe, and the strength of an allergic reaction is not necessarily linked to the amount of foreign protein you were exposed to.

Food intolerance, on the other hand, involves the digestive system alone: You are unable to digest a food you’ve eaten. The severity of your symptoms are directly related to the amount consumed of the offending food. A person who is intolerant to the lactose found in milk, for example, may be able to use milk in coffee without any problem. But he or she will start to feel uncomfortable after consuming several glasses of milk.

Lactose intolerance is the most common of all food intolerances. Very often you will find people describing it incorrectly as a “milk allergy.”

Symptoms of Food Intolerance

Food intolerance symptoms in most instances very specifically pertain to digestive system processes. People may experience heartburn that goes on to develop into bloating and stomach pain. They may complain of headaches and nausea, and begin vomiting. Gas, cramps and diarrhea quickly follow. In up to 45 percent of all people who suffer from food intolerance, symptoms can progress to more serious conditions like migraines, eczema and irritable bowel syndrome. 

How Do You Diagnose Food Intolerance?

Most food intolerance is not diagnosed through a visit to a health care provider, but discovered by the person experiencing the symptoms, generally through a process of trial and error. 

When people do visit physicians or dieticians, they may be asked to keep food diaries in which they list the foods they eat and any changes in their normal digestive habits that accompany the consumption of that food. Occasionally, a health care provider will suggest an elimination diet in which many foods are eliminated from the diet and then slowly reintroduced, one at a time: When symptoms reoccur, the offending food can then be identified. 

Treatment For Food Intolerance

Treatment for food intolerance generally involves avoiding foods you know will trigger digestive upset and treating symptoms when they do occur palliatively.

In some situations, however, as with lactose intolerance, dietary supplements have been developed which aid in the digestion of the trigger food. People suffering from lactose intolerance, for example, have their choice of buying “low lactose” milk-based products, or taking lactose-enhancing digestive enzymes if they want to drink milk.