The radio-allergo-sorbent-test (RAST) and skin prick tests are common
methods for the identification of occupational allergens, but only for
a few occupational allergens RASTs are available. Therefore often the
skin prick test becomes important for the diagnosis of a immediate ty
pe allergy. Skin prick testing is difficult, if the allergens or hapte
ns are hardly water soluble, as the dicarbonic acid anhydrides. We rep
ort about a practicable skin prick test using acetonic solutions of th
e haptens. Skin prick tests were performed with 1 and 5% acetonic solu
tions of phthalic anhydride (PA) and with the solvent acetone. We exam
ined 116 persons, who had been occupationally exposed against acid anh
ydrides and 20 persons without occupational exposure. RASTs with a con
jugate of PA and human serum albumin were carried out in the serum of
all persons with occupational exposure. The results of 16 skin prick t
ests and 13 RASTs were regarded to be positiv. The results of the skin
prick tests were comparable to those of the RAST. None of the 136 per
sons showed a positiv reaction to the solvent acetone in the skin pric
k test and no positive reaction was observed by testing the 20 occupat
ionally non exposed persons. In 7 challenge tests the clinical relevan
ce of a positive skin prick test and a positive RAST could be confirme
d.