If you have a reaction every time you eat a certain food, you may believe you have a food allergy. Food allergies are caused when the body’s immune system responds to a food as though it was a threat. You can read more about how food allergies happen in the food allergy overview.
Where symptoms occur
It is important to know that not every reaction to food is caused by a food allergy. Food allergies can cause a reaction anywhere in the body because allergen antibodies travel through the blood stream. So food allergies can cause hives, sinus problems, and stomach discomfort. Food intolerance is more likely to cause a reaction in the digestive tract – the stomach or intestines. Food intolerance can sometimes cause as strong a reaction to food as a food allergy. Food intolerance may cause symptoms soon after a food is eaten or symptoms may be delayed for several days. Food allergy symptoms often appear as soon as the food is eaten. The most severe food allergy reactions may cause anaphylaxis which is a swelling of the airway and sudden drop in blood pressure that can very quickly be deadly.
Symptoms over time
Because of the rapid onset of symptoms, food allergies are most often diagnosed in children, although some cases are not diagnosed until adulthood. Food allergies typically remain the same over time, while food intolerances can build up over time and become gradually worse. In some cases, a particularly stressful event may seem to trigger the onset or sudden worsening of food intolerance symptoms.
Immune system involvement
The most significant difference between food allergy and food intolerance is that the immune system is not involved in intolerance. Food intolerance is often caused by something that is lacking in the body’s digestive system that limits the ability to digest certain foods. For example, someone with lactose intolerance does not have the enzyme necessary to digest dairy foods. Approximately 75 percent of people have some type of food intolerance while only about 1 percent have food allergies.
Types of food intolerance
It is important to talk to your doctor about any symptoms you believe are associated with the foods you eat. Before diagnosing food allergy, your doctor may consider this list of possible food intolerances:
• Food poisoning – Food that is contaminated by bacteria or other toxins can produce symptoms similar to those of a food allergy.
• Histamine toxicity - Histamine is a substance that causes allergic reactions. Histamine levels can build up in some foods such as cheese, some wines, and certain fish (especially fish that has not been refrigerated correctly). If you eat a food that contains a high level of histamine, you can have a reaction that is similar to an allergic reaction. In this case, the reaction, known as histamine toxicity, is caused by the abnormal levels of histamine, not by the actual food product.
• Lasctose intolerance – Approximately one in 10 people is lactose intolerant. The enzyme lactase is normally produced in the lining of the stomach and is used to digest lactose, which is the sugar found in milk and most milk products. A person who is lactose intolerant does not produce enough lactase.
• Food additives – In order to make processed foods more appealing, food additives such as MSG are sometime added to foods to improve the flavor, add color, or limit the growth of microbes in the food. Eating large amounts of food containing certain additives can cause a reaction in some people.
• Sulfites – Some foods naturally contain sulfites and other foods have sulfites added to increase crispness or prevent the growth of mold. Large amounts of sulfites in foods can trigger asthma attacks in some people.
• Gluten intolerance - This intolerance is the cause of “celiac disease”. People with gluten intolerance are not able to digest gluten, which is a part of wheat and some other grains. Gluten intolerance does involve an abnormal response by the immune system, but it does not involve the IgE antibody which is normally involved in an actual food allergy.
• Psychological causes - Some people who had an particularly unpleasant experience that they associate with eating a certain food or meal will continue to have symptoms every time they eat that food. This is considered a psychological trigger rather than a physical cause.
• Other causes – Ulcers and certain cancers can also cause symptoms that are similar to those experienced with food allergies.
If your doctor rules out food intolerance and other causes for your symptoms, the next step may be testing to see if your body is producing the antibodies associated with a food allergy.