A food allergy is present when the immune system has an abnormal reaction to proteins in a particular food. Food-allergy symptoms, which can be triggered by ingesting even minute amounts of the food, usually happen within minutes but may, occasionally, happen a few hours later. Food allergies can begin in childhood or in adulthood, with some people suddenly having allergic responses to foods that have never caused problems. In other cases, allergies appear after a food is consumed for the first time. Certain food allergies that affect young children may eventually go away.
Causes of Food Allergies
A food allergy is caused by the immune system incorrectly identifying a particular food as a potentially dangerous foreign substance. This initiates a reaction in which antibodies are produced to combat the allergen. Afterwards, whenever that particular food is eaten, the antibodies respond by triggering the release of histamines and other chemicals throughout the immune system. It is these chemicals that are responsible for the various symptoms food allergies produce.
Types of Food Allergies
People can be allergic to any type of food, however, the most common foods that cause allergic reactions include:
- Cow's milk
- Tree nuts
Some people may also experience allergic reactions to food additives such as tartrazine, a food coloring, and aspartame, an artificial sweetener.
Symptoms of Food Allergies
Food allergies produce a wide range of symptoms. They may be relatively mild, causing only discomfort, or severe enough to be fatal. Symptoms of a food allergy may include:
- Itchy and/or flushed skin
- Vomiting, abdominal pain and diarrhea
- Sneezing, runny nose and congestion
- Itchy or watery eyes
- Swelling under the skin (angioedema)
In more severe cases, symptoms may include:
- Swelling of the throat, and hoarseness
- Difficulty breathing, and wheezing and chest tightness
- Dizziness or loss of consciousness
- Anaphylactic shock
If an anaphylactic reaction occurs, emergency medical care should be sought immediately. Delaying treatment can result in coma or even death.
Risk Factors Associated with Food Allergies
Certain people, especially children, are more likely than others to develop food allergies.The risk for developing a food allergy may be greater in people with:
- Other allergy-related conditions such as eczema or asthma
- A history of food allergies, even if symptoms have disappeared
- A family history of food allergies or other types of allergic reactions
Food allergies generally develop early in life but can develop at any age.
Diagnosis of Food Allergies
Any time an allergic reaction occurs, an appointment should be made with an allergist in order to identify the source or cause of the allergy. Accurate diagnosis of true food allergies is important to prevent future allergic reactions. An allergist will be able to diagnose a food allergy by taking a patient's complete history, and performing skin testing and blood testing. Occasionally, an allergist-supervised "food challenge" may be required to confirm the diagnosis.
Many people who experience reactions to foods have an intolerance to them rather than a true allergy. For example, lactose intolerance from milk is easily confused with a milk allergy. Food intolerance frequently has symptoms similar to those of a food allergy, especially if there is gastrointestinal distress involved. However, people with food intolerance can often safely eat a small quantity of the problematic food without having a reaction. In contrast, a person with a true food allergy typically cannot consume any amount of the trigger food without developing symptoms.
Treatment of Food Allergies
The most effective treatment for a food allergy is strict avoidance of the problematic food. Checking ingredient labels is extremely important, as is asking about ingredients in food prepared in restaurants and at the homes of others.
For someone who has only mild allergic reactions, an antihistamine may be an effective treatment for relieving symptoms. In severe cases, when severe allergic reactions occur, immediate medical attention is required. For severe allergies, an allergist will prescribe an injectable epinephrine (self-injection pen) that can be carried at all times. There is no cure for food allergies, although most children usually outgrow allergies to milk, eggs, soybean products and wheat.