Food Allergies

Food Allergies

In most people, food can be eaten without any problem. If a person is allergic to a certain food they can have a mild to severe allergic reaction. The person has developed antibodies to the food, and when even the smallest amount of this food is eaten, the body’s immune system begins to defend itself from the food it thinks is harmful. It releases antibodies known as immunoglobulin E (lgE) antibodies to neutralize an allergen. A chemical called histamine, along with other chemicals, is released into your blood stream. This causes an allergic response that include a dripping nose, itchy eyes, dry throat, rashes and hives, nausea, diarrhea, labored breathing, and even anaphylactic shock.

A food allergy can begin at any age, but often starts in childhood. About 5% of children and about 4% of teens and adults actually have a clinically proven allergic reaction to foods. Many children who have a food allergy to milk, eggs, wheat, and soy outgrow the allergy by the age of 5, if they avoid the food. Allergies to peanuts, tree nuts, and shellfish tend to be a lifelong allergy. In older children and adults, the most common food allergies are:

  • Fish
  • Peanuts (and peanut butter)
  • Shellfish
  • Tree nuts
  • Food additives – such as dyes, thickeners, and preservatives

In some people, a food allergy can trigger a severe allergic reaction called anaphylaxis. Life-threatening symptoms can occur within 2 minutes, and include:

  • Constriction and tightening of airways
  • A swollen throat or the sensation of a lump in your throat that makes it difficult to breathe
  • Rapid pulse
  • Dizziness, lightheadedness or loss of consciousness

Emergency treatment is critical for anaphylaxis. If untreated, it can cause coma or death.

An allergy syndrome, called a pollen-food allergy, affects the mouth and tongue after eating certain fresh fruits and vegetables. The throat can swell or even anaphylaxis. Proteins in fruits and vegetables cause the reaction because they are similar to those allergy-causing proteins found in certain pollens. Melons, for example, contain substances similar to rag weed pollen, and apples have allergens similar to tree pollen.

Many people do not have a true allergic reaction to a certain food, but rather have food intolerance. Most intolerance symptoms are caused by food like corn products, cow’s milk and dairy products (lactose intolerant), or wheat and other gluten-containing grains. In a true food allergy, the immune system produces antibodies and histamine in response to the specific food.

Diagnosis/Testing

To determine if there is a food allergy, a doctor must first find out if the patient is having a harmful (adverse) reaction to a specific food. This includes a patient history and information on what foods are eaten. The next step is to eliminate the food from the diet. If the symptom goes away, it may be the food. If the food is eaten again, and the symptom returns, then the food can be confirmed as the cause of the allergic reaction.

A skin prick test can be more realistic in determining a food allergy. Skin tests are rapid, simple, and relatively safe. The skin is pricked with a needle to allow a tiny amount of the suspected food beneath the skin’s surface. If a raised bump or reaction develops, it shows an allergy. A positive skin test, along with the history of the allergic reaction to the food eaten, are both considered in the doctor’s decision that it is a food allergy.

Patients who have had severe anaphylactic reactions may not be able to have skin tests because it could cause a dangerous reaction. For these patients, blood tests such as the RAST and ELISA can be done to determine the allergy.

The RAST blood test measures the amount of allergen-specific lgE in the blood to detect an allergy to a particular substance. Each allergen-specific lgE antibody test is separate and very specific–such as testing the egg white and then testing the egg yolk. If allergen-specific antibodies are found, allergies are suspected. Having lgE antibodies may only mean that you are sensitized to the allergen. You were exposed, but you may not be allergic. The RAST test should be compared to your history of allergies.

The RAST blood test can be done thru this office. Call (865) 546-3998 to schedule an appointment.

Treatment

The only proven treatment for a food allergy is to avoid the food. People with food allergies should learn to read food labels carefully to check the ingredients, including any foods that may contain the ingredient (such as recipes) and processed foods prepared in plants where the ingredient was used for other foods.

There are several medications that can relieve food allergy symptoms. These include antihistamines to relieve gastrointestinal symptoms, hives, or sneezing and a runny nose. Other treatments, including allergy shots and probiotics, have not been clearly proven to help with food allergies.

People diagnosed with a food allergy should carry, and know how to use, an injectable epinephrine pen called an “Epi Pen” at all times. This pen contains a medication that can be quickly self-injected for a severe allergic reaction.

Consider having your child see an allergist for any suspected food allergy, and meet with one of our dieticians for a nutritional consult. Call (865) 546-3998 to schedule an appointment.