Allergy Testing for Asthma

(LifeWire) - Allergy testing may be recommended for people with asthma, because allergies can play a significant role in causing asthma symptoms. Skin tests, blood tests and elimination diets are the most common and effective ways to diagnose allergies and allergic asthma.

Approximately 20% of adults and children in the U.S. have allergies. Children are more susceptible to allergic reactions than adults, and approximately 80% of children with asthma also suffer from allergies.

What are Allergies?

An allergy refers to the way the body's immune system reacts to triggers in the environment, such as foods, dust mites, animal dander and pollen. Allergic symptoms appear when an environmental trigger spurs the body to release antibodies known as immunoglobulin E (IgE), which in turn causes chemicals to be released. Depending on the allergy and its trigger, these chemicals can cause symptoms of an allergic reaction that include the following:

• Red, itchy bumps on the skin
• A runny nose
• An upset stomach, cramps, bloating or diarrhea
• Wheezing or difficulty breathing
• Itchiness or swelling of the lips, tongue or throat
• Anaphylactic shock -- an extreme, life-threatening reaction that requires immediate medical attention

Some doctors believe that recurrent ear infections in children may also be related to allergies.

Testing for Allergies

Allergies can be diagnosed in several ways. Sensitivity to specific allergens can be determined by both individual and family medical history of allergies and asthma, a physical exam or allergy tests.

• Allergy Skin Prick Test – The skin prick test is the most common allergy test. With this test, small amounts of an allergy trigger are given by pricking or puncturing the skin on the arm or the back with a needle or similar device. The two most common types of skin pricks are the percutaneous method and the intercutaneous method.

  Using the percutaneous method, the doctor will place a drop of each allergen extract on the skin or directly on one or more needles or clusters of needles. Then the top layer of skin is pricked, punctured or scratched so that the extract can seep in. Using the intercutaneous method, the doctor injects the allergen extract underneath the first few layers of skin. This is done with a syringe and a very fine needle.

  If an individual is allergic to that substance, a reaction in the form of a wheal -- a red, itchy bump -- usually appears within 15 minutes. The bigger the bump, the more sensitive the person is to that specific allergen. Skin prick tests do not take much time and are the least expensive of allergy tests. The procedure is not painful.

• Allergy Blood Test – Allergies can also be determined by blood tests, such as the radioallergosorbent test (RAST) and other blood tests that use radioactive or enzyme markers to determine whether IgE antibodies are present. Blood tests are used when a skin test is difficult because of an existing skin condition -- such as a rash or eczema -- or when the person is afraid of needles or when there is the possibility of a severe allergic reaction.

  Skin tests and blood tests can both diagnose allergies, and both are considered accurate approximately 90% of the time.

Food Allergies and the Elimination Diet Test

Food allergies can be diagnosed through an elimination diet in which suspected foods are eliminated from the diet for a period of four to seven days. More than 80% of those with food allergies are allergic to one or more of the following food sources: milk, soybeans, eggs, peanuts and other nuts, wheat, shellfish or corn.

If the allergic reaction does not cease during the elimination diet, additional foods are withdrawn until symptoms do stop. At that point, new foods are added back into the diet until the symptoms reappear.

The main problem with an elimination diet is making sure packaged or processed foods are closely checked. Many common food allergens can be found not only in their natural state, but they may also be hidden in other foods as well.

Who Conducts Allergy Tests?

Allergy tests are usually performed by an allergist who is a physician specializing in diagnosing and treating allergies. To find a board-certified or pediatric allergist, contact the American Academy of Allergy, Asthma & Immunology or the American College of Allergy, Asthma & Immunology.

Treating Allergies

If tests indicate specific allergies, the doctor will recommend a treatment plan that may include allergy shots, which is also called immunotherapy. Allergy shots consist of a serum that contains very small amounts of the specific allergens. As a result of receiving these injections at regular intervals for a period of time, the body's immune system is built up to lessen the allergic response to these allergens.