In San Antonio Texas, all Allergists initially perform routine testing for sensitivity to allergens in the air and for food allergy by skin prick (scratch) testing. With prick/scratch testing there is no deep penetration of the skin, and bleeding is not typically seen. Although there is a sharp pinching sensation, most persons describe the procedure as only mildly uncomfortable.  Occasionally, intradermal skin testing is performed in which the allergen is injected under the skin with a needle. Intradermal testing is significantly more painful that scratch testing and a small amount of bleeding is occasionally seen with this technique. It is believed by the JTF that intradermal skin testing places the patient at an increased risk for anaphylaxis but this testing may, in some rare instances, provide information concerning allergic sensitivity that was not detected by the scratch test. As per the JTF, intradermal skin testing interpretation is more likely than prick testing to yield inaccurate (false positive) result. The decision to perform intradermal testing is made by the physician only after carefully considering the risk versus benefit to the patient. Due to patient safety concerns, the JTF does not recommend initial screening for any possible allergic sensitivity by intradermal testing before prick testing is performed.  Intradermal testing for food allergy is considered by the JTF to be too dangerous to justify its use under any circumstance. *Both the JTF and the local community of Allergists recognize that both blood testing (RAST) and intradermal skin testing for allergic sensitivity impose a significantly increased cost of medical services on both the consumer (patient) and the healthcare insurance providers. To help keep healthcare costs affordable, Allergists are dedicated to limiting the use of these two testing options whenever possible.   

A physician performing skin testing is legally and ethically responsible for the training and actions of the medical staff he supervises. All Allergists train their own medical staff in the appropriate use of allergy testing and in its correct interpretation. To avoid patient misdiagnosis, it is critical for any physician performing skin testing to have verified the accuracy of the skin testing device being used and to have confirmed the competency and reliability of the test operator (typically their staff). It is always advisable to ask your physician if he or she was trained to perform any test they may recommend. *Medicare guidelines require the physician performing a skin test to personally examine and grade the results. All allergy skin tests should include a negative control (saline or diluent) that shows what type of reaction occurs on the skin as a result of irritation caused by the testing devise alone.  All allergy skin tests should also include a positive control called histamine. Histamine causes itching and produces a skin reaction that mimics an allergic reaction. As per the JTF guidelines, for any skin test to be considered valid, the histamine control test should show reactivity (redness and / or swelling) at least 3mm larger than the negative control. If the skin test is being graded by measuring the size of the skin reactions, studies have shown that an “allergic” reaction to a skin test allergen is likely to be present if the reaction size is also at least 3mm greater than the negative control.