Introduction to in vivo allergy testing.

Available in vivo skin tests for assessment of hyperreactivity are essentially similar in principle, in that they rely on the reactivity and sensitivity of dermal mast cells sensitized with specific immunoglobulin E to reflect allergic sensitivity. In this article the immunology of skin testing is examined and the various factors that may influence reactivity are noted. In addition, the respective benefits and drawbacks of such familiar epicutaneous skin tests as the scratch and prick tests and intradermal (or intracutaneous) methods, including skin end point titration, are explored. Efforts to standardize testing technology are also discussed. It is concluded that each method of in vivo skin testing is associated with both advantages and disadvantages and that the most important factors are sensitivity and reproducibility.