While your child’s history and physical examination provide evidence that she has an allergic disorder, they may or may not provide clues to the specific allergens that are provoking the reactions. This information can be very useful in suggesting whether or not changes in the home environment would reduce or eliminate allergic symptoms. It might also provide the basis for a form of treatment known as immunotherapy.
If your child’s symptoms are particularly bothersome or persistent, unresponsive to medications, or severe (for example, wheezing episodes requiring repeated medical intervention), the physician or allergist might recommend skin tests to help identify what might be triggering these allergic responses. The testing involves pricking the skin on the back in several places, and in doing so, exposing these areas to substances that might provoke an allergic reaction. If your child is sensitive to a particular substance, a local reaction (redness and itching) will develop within several minutes. Occasionally certain substances may be injected directly into the outer layer of the skin, a process called intradermal testing. This is usually done when the child’s history raises suspicions that one or more substances might be involved in her allergies but prick tests using those substances are negative.
Another option is the measurement of immunoglobulin E (IgE), a specific antibody produced when an allergen enters the body. Blood tests can determine elevated levels of immunoglobulin E as well as the amount of antibody that has been produced against specific allergens such as grass, animal hair, or rag weed.