What is an Allergy?
An allergy is the body's immune system response to specific elements in the environment. Children with allergies react to certain substances in their everyday environment, which usually don't cause reactions in other children.
About 20 percent of Americans—one in every five adults and children—have allergies, including allergic asthma. About 80 percent of children with asthma have allergies. Food allergies occur in 8 percent of children younger than age six.
How do Allergies Affect Children and How do They Get Them?
Children seem to be more vulnerable to allergies than adults. Allergies to food, house dust mites, animal dander and pollen are most common. These allergies show up as allergic rhinitis (hay fever), asthma, and atopic dermatitis (eczema). Also, frequent ear infections may be related to allergy.
If both parents have allergies, their (biological) child has a 75 percent chance of having allergies. If one parent is allergic, or if relatives on one side of the family have allergies, then the child has about a 50 percent chance of developing allergies.
There is some evidence that breast-feeding helps prevent children from developing food allergies and eczema.
What are Signs or Symptoms of Allergy in a Child?
Symptoms develop as the body releases special antibodies called IgE (immunoglobin E), which are the key players in allergic reaction. These special antibodies can trigger the release of chemicals that can cause the physical symptoms and changes associated with allergies such as:
Itching or swelling of the lips, tongue or throat
Upset stomach, cramps, bloating or diarrhea
Wheezing or difficulty breathing
Anaphylactic shock — a life-threatening body reaction requiring emergency care
What Tests are Generally Used to Diagnose Allergies?
First, keep in mind that allergy tests are not the sole basis for diagnosing or treating an allergy. Health care providers make an allergy diagnosis based on several factors:
History of the child's experiences and family history of allergy/asthma
Physical exam of the child to detect signs of allergy
Allergy testing for sensitivity to specific allergens
Allergy tests help your physician confirm allergies your child may have. When an allergy test pinpoints a reaction to a specific allergen(s), your health care provider also can use this information in developing "immunotherapy" — allergy shots — specifically for your child, if appropriate.
Skin Tests for Allergies
Skin prick tests are the most common tests for allergy. Small amounts of suspect allergy triggers are introduced through the skin of the arm or back by pricking or puncturing the skin with a needle or similar device. If your child is allergic to a substance, you will see a raised, red itchy bump, also called a "wheal." Reactions usually appear within 15 minutes. This positive result indicates that the IgE antibody is present when your child comes in contact with the specific allergen. The size of the wheal is important: the bigger it is, the more sensitive your child is to that particular substance. This test is the least time consuming and expensive. You may have to discontinue certain medications, especially antihistamines, several days prior to testing.
There are four kinds of skin tests: scratch, puncture, prick and intradermal. Your allergist may use one or more skin tests to analyze your child's response to various substances. Keep in mind that you may see a false-positive or a false-negative skin test. Results often depend on how well the test is performed.
Skin prick, puncture and intradermal tests may be difficult with young children afraid of needles. There is some possibility of a life-threatening anaphylactic response if a person is extremely sensitive to a substance. Your health care provider will be prepared to react swiftly to this kind of response.
Blood Tests for Allergies
The RAST (radioallergosorbent test) and related blood tests use radioactive or enzyme markers to detect levels of IgE antibodies. These tests are useful when a skin test is difficult due to a widespread skin rash, anxiety about skin pricks, or if the child has the potential for a sudden and severe allergic response to test allergens.
Skin tests and these blood tests are very comparable in their ability to diagnose sensitivity to specific allergens. Both kinds of tests are considered to be about 90 percent accurate.
An elimination diet is often used to help isolate sensitivity to specific foods. Your health care provider sets up a diet without foods that you suspect may affect your child. Because milk, soybeans, eggs, wheat, peanuts, nuts, shellfish and corn are the main culprits for more than 80 percent of people who have food allergies, these foods are usually not included in the starting diet.
Your child will stay on the prescribed diet for four to seven days. If the symptoms do not subside, additional foods are eliminated until the allergy symptoms stop. Once the symptoms disappear, new foods are added to the basic diet, one at a time, until symptoms reappear.
The chief drawback to an elimination diet is making sure your child is eating "pure" foods. Common food allergens are "hidden ingredients" in hundreds of packaged or processed foods. In order for an elimination diet to be successful, check ingredients for foods you give your child to eat. If your child is a fussy or picky eater, an elimination diet can be difficult. Your health care provider can suggest helpful approaches.
Fasting is a radical way to identify food allergies. Although very effective for detecting problem foods, this kind of elimination diet is hard to do with children. Fasting is best done under medical supervision and often is used for "extreme" cases where a child is suspected to have allergies to many types of food.
Are There Other Allergy Tests?
The tests described above are considered the most effective and usual way to help diagnose allergies to specific substances. You also may hear of other allergy tests. These tests may work, but as yet, they are unproven or not universally accepted allergy testing methods. If your health care provider suggests one of these tests, consider getting a second opinion about allergy testing for your child:
cytotoxicity blood test
sublingual provocative testing
candidiasis allergy theory
basophil histamine release
What Kind of Doctor Does Allergy Testing?
Allergy testing usually is done by an allergist. An allergist specializes in diagnosing and treating allergies. Some allergists specialize in treating children. To find a board-certified allergist or pediatric allergist near you, contact:
What can Parents do if their Child has a Positive Allergy Test?
A positive allergy test helps your physician figure out the best treatment plan for your child. The doctor may prescribe specific medicine for the allergy(s) and suggest ways to cut down or eliminate substances in your child's environment that can trigger an allergic response. Many allergies are mild to moderate. Most allergies are easily managed with the right treatment plan.
SOURCE: This information should not substitute for seeking responsible, professional medical care. First created 1995; fully updated 1998; most recently updated 2005.
© Asthma and Allergy Foundation of America (AAFA) Editorial Board