Reactions to foods can be divided into two main groups:
Food Allergy: this is a reaction that involves the immune system.
Food Intolerance: does not involve an immune response, but can produce symptoms that are similar to allergic reactions.
Most true food allergies develop in childhood, and can often be seen within the first year of life. Some of these allergies can diminish with age, although they can also persist into adulthood.
The major food allergens seen in children are:
- Tree nuts
The major food allergens seen in adults are:
- Tree nuts
There are a variety of symptoms that can result from having a Food Allergy. These can include features from one or more of the following groups, and can vary from reaction to reaction:
- Gastrointestinal: nausea, abdominal pain, cramping, vomiting and diarrhea after eating certain foods.
- Oral: itching and swelling of the lips, tongue, and throat after eating certain foods.
- Respiratory: nasal congestion, runny nose, sneezing, itching, coughing, hoarseness/voice changes, wheezing, as well as eye lid swelling and redness, and eye watering/itching.
- Skin: urticaria (hives) and angioedema, as well as worsening of eczema.
- Anaphylaxis: this reaction is considered potentially life threatening, and can include any of the above listed symptoms, in addition to low blood pressure, abnormal heart rate, and shock. Patients are at higher risk of having anaphylactic reactions to foods if they also suffer from asthma, if they accidentally eat the problem food, or have a history of having allergic reactions to certain foods in the past.
Food Intolerances involve a wide variety of outcomes, including:
- Celiac disease: a sensitivity of the intestine to gluten, which is found in oats, wheat, rye and barely. Results in diarrhea, bloating, gas, weight loss, and occasionally nausea and vomiting.
- Toxic reactions: contamination of foods from bacteria or chemicals. Less common are reactions to MSG, sulfites, and aspartame.
- Lactose intolerance: a very common occurrence, this reaction involves lactase deficiency. Lactase is involved in breaking down lactose, the major sugar found in dairy products. When lactase is not present in the body, the small intestine cannot absorb lactose. Bacteria normally found in the intestine causes the lactose to ferment, causing bloating, gas, cramps and diarrhea.
Evaluation of food allergies, like other allergies, involves taking a thorough history complete with description of the problem, specifically the suspected food(s). Also important is a detailed report of the timing of events surrounding a reaction, the symptoms involved, and length of time since the last reaction occurred. Depending on the history given by the patient, further evaluation can include skin prick testing, RAST testing (by blood), food diary, elimination diet, and oral challenge.