Allergies may be tested using skin or blood tests. Skin testing is the most common. Depending on the allergy, we may recommend skin tests, blood tests, or both. There are two types of skin tests. The most common testing for many typical allergies is done by pricking the skin with a small amount of the allergen. Often, several of these are done at once, on the patient’s back. Allergic sensitivities show with redness and swelling at the test site.
When a single allergy sensitivity is tested, a small amount of the suspected allergen may be injected into the skin on the patient’s arm. Results from skin testing are usually apparent within 20 minutes. In rare cases, a delayed reaction may appear 24-72 hours after the test. These should be reported to your health care provider when they’re noted.
Since blood testing requires lab analysis, it may take some time for results to return. However, blood testing is often necessary when the patient is taking medication that may interfere with skin tests. A skin condition such as psoriasis or eczema may make skin test assessments difficult. In general, young children don’t tolerate skin testing as well as older children and adults, so a single blood sample may be less traumatic.
When strong allergic reactions are being assessed, working from a blood sample can potentially be safer than skin testing. When it comes to allergies, no test is perfect and both skin and blood tests may produce false results or results that are not definitive. Allergy testing is part of the diagnosis tool kit, along with your caregiver’s observations and your medical history.
Allergies have two general treatment approaches. Symptomatic treatment uses medication to address the reactions to an allergen. For example, allergies such as hay fever that produce itchy eyes, runny nose, and sneezing may respond to antihistamines and decongestants. This technique provides relief from the symptoms, but doesn’t address the allergy itself.
To address the underlying allergy, immunotherapy is used. By incrementally increasing a patient’s exposure to an allergen, the body’s immune system has time to build natural defenses against the allergen in question. As the immune system creates antibodies, the effects of the allergen reduce in intensity. Immunotherapy is usually done through injection, the common being allergy shots. Some oral medications, dropped or dissolved under the tongue, are emerging as an alternative for some allergies because of the ease and convenience.
For some allergies, just knowing is power. Allergy testing can help you develop avoidance behaviors to prevent reactions. For instance, if you woke up every morning with allergies and found out that you had allergies to feathers, changing from a down pillow to another material may have a profound effect on your health.