Credit for the first skin testing device goes to Charles H. Blackley, who in 1865 abraded a quarter-inch area of skin with a lancet, producing a dermatographic reaction. He then applied pollen grains that had been placed on a piece of wet lint and covered the scarified area with an occlusive bandage. This resulted in intense itching and a very large response with swelling that was maximal at 2.5 by 1.5 inches by the end of 6 hours.<sup>26 Taylor G., Walker J. Charles Harrison Blackley Clin Allergy 1993 ;  3 : 103-108

Cliccare qui per andare alla sezione Riferimenti</sup> Further historical aspects of skin testing are reviewed by Cohen elsewhere in this issue.

Early clinicians used the von Pirquet borer for epicutaneous testing as well as other devices. In 1924, Lewis and Grant first described the prick skin test method,<sup>14 Lewis T., Grant R.T. Vascular reactions of the skin to injury. Part II: The liberation of histamine-like substance in injured skin, the underlying cause of factitious urticaria and of wheals produced by burning, and observations upon the nervous control of certain skin reactions Heart 1924 ;  11 : 209

Cliccare qui per andare alla sezione Riferimenti</sup> but scarification methods and intradermal testing were advocated emphatically by most clinicians in the United States. In a 1931 report, Rappaport described a multiple scarifier—the Mueller device.<sup>24 Rappaport B.Z. A multiple scarifier for allergic tests J Allergy 1931 ;  2 : 379-380  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> He noted that a significant problem with the scarification technique was a lack of uniformity in the abrasion. The Mueller device was designed to make six uniform abrasions 1.5 mm long and 15 mm apart. This level of uniformity was thought to be a great innovation in the attainment of reproducible skin testing. Also, this device seemed to reduce the pain associated with the skin testing procedure.

In 1950, Squire reported use of a straight Hagerdorn-type surgical cutting needle (about 5 cm long) for prick skin testing.<sup>25 Squire J.R. The relationship between horse dandruff and horse serum antigens in asthma Clin Sci 1950 ;  9 : 127

Cliccare qui per andare alla sezione Riferimenti</sup> He described a technique in which the noncutting portion of the needle was held between the forefinger and thumb, allowing friction to give fine control in the degree of penetration when the needle was plunged through the drop of test material into the skin while attempting to avoid bleeding. Pepys' description of the modified prick skin test method in 1968 renewed interest in this technique.<sup>22 Pepys J. Skin testing in diagnosis Clinical Aspects of Immunology Oxford, UK: Blackwell Scientific Publications (1968).  192

Cliccare qui per andare alla sezione Riferimenti</sup> He used a hypodermic needle (40 mm long × 0.8 mm diameter) that was directed through a drop of extract at an angle of 60° to 70° to the skin. With the needle point only catching the skin and lifting it, a canal is made through which the extract can enter the skin. The needle is then pulled out carefully in the inverse direction, and the drop of extract is wiped.

In the 1970s the scarification method continued to be used with such devices as the Cross scarifier (Hollister-Stier Laboratories of Canada). Studies comparing scarification with prick skin testing demonstrated increased false-negative and false-positive results in scarification.<sup>11 Imber W.E. Allergy skin testing: A clinical investigation J Allergy Clin Immunol 1977 ;  60 : 47-55  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 12 James J.M., Simon F.E. Allergy skin testing: Comparison of conventional and new techniques CMAJ 1979 ;  120 : 330-332

Cliccare qui per andare alla sezione Riferimenti</sup> As a result of such studies, use of the scarification technique diminished.