Food allergy occurs when the body’s immune system reacts to an allergen in a food that is mistakenly seen as harmful. When exposure to the food in question occurs, the immune system sees the allergen as a threat, and attacks it. Typically, the allergen is a food protein. These food allergies are caused by abnormal production of allergy cells(IgE antibodies) that are formed against these food proteins or allergens. When exposed to the allergen, IgE antibodies cause the release of histamine and other allergy chemicals that lead to the characteristic allergic reaction.
Symptoms of food allergy
Symptoms can be mild with rash or hives, swelling usually of the face, hands and feet, itching, runny nose, nasal congestion, sneezing, itchy, watery eyes, nausea, vomiting, and diarrhea.
More severe symptoms can include trouble breathing with coughing, wheezing, shortness of breath, chest tightness, decreased blood pressure or hypotension, feeling of impending doom, loss of consciousness, anaphylactic shock, and even death.
Foods that cause food allergy
Any food is capable of causing food allergy. However, the eight most common food allergens make up 90% of food allergy cases:
- Tree nut
The most common food allergens for children are milk, egg, wheat, soy, peanuts and tree nuts.
Adults are more likely to be allergic to peanut, tree nut and seafood (shellfish).
Around 80% of children with egg or milk allergy will outgrow this sensitivity by early elementary age. On the other hand, less than 25% of children with peanut allergy will eventually become tolerant of peanut. Most adults with late development of food allergy to peanut, tree nuts or seafood do not lose their allergic sensitivity.
Who gets food allergy?
Food allergy is seen in 5-8% of children with a peak in the first two years. Overall prevalence is 3% for all ages. Children with eczema have a 35-40% risk to develop food allergy.
Children with food allergy, in particular egg allergy, have at least a 50% chance to develop allergic rhinitis and asthma. Milk is the most common food allergen in general, and 50% of milk allergic children will be allergic to some other food allergen. One-third of peanut allergy patients will have allergy to other nuts.
Diagnosis of food allergy
Food allergy is diagnosed by a thorough history, exam and appropriate diagnostic testing.
Sometimes the food allergen in question is easy to uncover, but this is not always the case.
Allergy skin testing is the most accurate, safe, and cost effective way to identify food allergens. Blood tests or serum-specific IgE food tests can also be utilized in cases where skin testing is not feasible. Serum or blood allergy tests can be expensive and are less sensitive, difficult to interpret, carry increased costs, and often take several days to get results.
When necessary, oral food challenge is performed to confirm a specific food allergy diagnosis.
Oral challenges can also be utilized to establish that the patient has developed a tolerance to a certain food allergen. Oral challenges should only be performed in a medical facility by a board certified allergist who is trained in such procedures.
Treatment of food allergy
There is no current cure for any food allergy. The most important treatment is AVOIDANCE!
All patients should strictly avoid all food allergens, and take necessary precautions at home, school, work and social environments. All food allergy sufferers should carry an epinephrine device such as an Epipen with them at all times or should have such a device readily available.
If you ever need to use your Epipen, go immediately to the nearest emergency medical facility for further evaluation and treatment. The action of epinephrine only lasts for 15-20 minutes, so
it is imperative to be evaluated in the ER after use. In addition, it is believed that 25% of severe allergic reactions have a biphasic or second wave of allergic symptoms. This is another reason to be seen in the ER following an allergic reaction. Seeing a registered dietician with special training in food allergy can be very helpful with label reading, substitution of non-allergenic foods, and nutritional adjustments in the patient’s diet to make up for nutrients lost with food allergen avoidance.
Oral Allergy Syndrome
Oral Allergy Syndrome is a form of food allergy that can be seen in pollen allergy sufferers who develop mild food allergic symptoms to certain fresh fruits and vegetables. These patients have mouth and throat itching and burning when eating the fresh foods.
Examples are tree pollen patients who experience oral allergy symptoms to fresh apple or peach, and the ragweed allergy patients who have mouth and throat itching with fresh melons or bananas. There are numerous other examples.
It is rare for these oral allergy patients to have severe reactions, but on occasion severe reactions have occurred. It is not normal to have these symptoms when eating any food.
You should tell your allergy provider of any unusual symptoms to any foods.
Alpha Gal Syndrome
Alpha gal syndrome is a delayed food allergy which is caused by a sugar called Galactose-alpha-1,3-galactose or Alpha gal for short. Most allergens are proteins, but this is an exception to that rule.
Several months after a bite from the lone star tick, patients begin having allergic reactions that are delayed to mammal meats and fats. Less commonly, these patients can also have reactions to milk and gelatin. Typical reactions occur 3-6 hours after ingestion of these meats including beef, pork, lamb, bison, and deer. In fact, Alpha gal can be found in the meat of any mammal except humans and great apes.
Reactions can be mild or can be very severe. Most commonly, these reactions start with palmer itching, followed by generalized hives, abdominal cramping, nausea, vomiting, diarrhea, and even respiratory symptoms and generalized anaphylaxis.
Treatment is strict avoidance of all mammal meats/fats and all patients need to carry and epipen or similar epinephrine device.