The general public often uses the term “food allergy” interchangeably with the term “food intolerance/sensitivity”. Though some of the symptoms of food intolerance and food allergy are similar, the differences between the two are very important. Eating food you are intolerant to can leave you feeling miserable. However, if you have a true food allergy, your body’s reaction to this food could be life-threatening.
A true food allergic reaction involves the immune system. Your immune system controls how your body defends itself. With food allergies, one’s immune system overreacts to an ordinarily harmless food. This is caused by an allergic antibody called Immunoglobulin E (IgE). After production, IgE binds to its receptors on mast cells and waits to be activated by the offending allergen. Once these cells are stimulated, it will burst open, leading to the release of chemicals, such as histamine. These chemicals create the typical symptoms of an allergic reaction. These antibodies can be activated with even the most miniscule amount of food (1/250th of a peanut is enough to trigger a reaction in some!) so “just a taste” is never safe for a person with food allergies. The most common food allergens – responsible for up to 90% of all allergic reactions – are the proteins in cow’s milk, egg, soy, wheat, fish, shellfish, peanuts and tree nuts.
Symptoms of a food allergy can be mild – such as a few hives, itching/redness of the skin or mild swelling (angioedema) – or they can be more severe. The most serious type of allergic reaction is called “anaphylaxis” and may involve the respiratory, gastrointestinal, and/or cardiac systems. Respiratory symptoms may include coughing, wheezing, throat tightness/swelling, and chest tightness (similar to asthma symptoms). There may also be swelling of the upper airway, causing stridor. Gastrointestinal symptoms of food allergies include vomiting, diarrhea and abdominal cramping, which may be severe. Cardiac symptoms can include dizziness/pallor, a loss of consciousness, or a drop in blood pressure (termed “anaphylactic shock”). These symptoms may occur alone, with no hives, or in combination with hives or angioedema (facial swelling). Without immediate treatment—an injection of epinephrine and expert care—anaphylaxis can be fatal.
The best way to prevent an allergic reaction is to strictly avoid foods that you know can cause a problem. Testing a child or adult for food allergies should be done by a board-certified allergist who can help interpret the results in context with the clinical history. An individual with a known food allergy, who has ingested the offending food and is exhibiting a mild reaction, should be administered an antihistamine, such as Benadryl, and monitored closely. For individuals displaying more of the severe symptoms, an epinephrine auto-injector (Epipen, Auvi-Q) should be used immediately.This is a self-injection device that allows quick injection into the outer thigh. The effects of epinephrine take action immediately, but wear off after 20 minutes, and sometimes further treatment may be necessary. This is why all persons who receive an epinephrine administration for a serious allergic reaction should seek immediate medical attention by calling 911 or going to their local emergency room.
Pollen-food allergy syndrome, commonly known as “oral allergy syndrome”, is a milder type of food allergy that many patients with nasal allergy experience. Common symptoms are itching or tingling of the mouth or throat after eating certain raw fruits and vegetables. While these allergies tend to be mild, rarely they can be life threatening. It can be difficult to differentiate oral allergy syndrome from more severe food allergies.
A food intolerancerefers to an abnormal response to a food that is not an allergic reaction. Unlike allergic reactions, this does not involve the immune system. Food intolerances are more common than food allergies, with over 30% of Americans believing they have an intolerance to one or more foods. Oftentimes, food intolerance responses take place in the digestive system where individuals are unable to properly breakdown a food. This could be due to enzyme deficiencies (ex: lactose intolerance), sensitivity to food additives (ex: MSG or artificial colors) or reactions to naturally occurring chemicals in foods (ex: jitteriness or insomnia with caffeine). Typically with a food intolerance, people can eat small amounts of the food without causing significant symptoms. Symptoms of sensitivity or intolerance to a food can vary, but are generally digestive related (abdominal pain, diarrhea, bloating, constipation, cramping, and nausea). A well-known example is lactose intolerance. Individuals with this disorder experience uncomfortable abdominal symptoms after consuming dairy products. This is due to an absence of an enzyme (lactase) necessary for proper digestion of the sugar in milk (lactose). These symptoms may easily be prevented by taking lactase enzyme pills or dairy products supplemented with lactase (ex: Lactaid).