Positive reactions to patch tests with neomycin and aminoglycosides

Abstract

The positive rate of patch test reactions to neomycin was studied for a period of 19 years. A patch test for 20% neomycin in white petrolatum was performed in 1867 cases of contact dermatitis or drug eruption. The comparison of this positive rate was made by dividing the 19 years into four periods. In the first period (1966-1970), the positive rate of patch test reactions to neomycin was comparatively higher than in the other three periods (p<0.01, x²-test). All of the positive patients tested had a history of neomycin use. After 1971, the frequency of positive reactions was stabilized at the rate of 3-5% in all of the patients tested : and also 1-3% in the patients with an obvious history of neomycin use. The difference in the frequency was considered to be caused by crosssensitization due to other aminoglycosides.
The positive rate of patch test reactions to the other aminoglycosides was also studied for 10 years (1975-1984). This patch test was performed in 473 cases of contact dermatitis or drug eruption caused by the use of antibiotics. The positive rate of patch test reactions to either one or more of the aminoglycosides was 11% (52 among 473 cases). As the positive rate of patch test reactions is not stabilized each year, there has been no obvious tendency of a gradual increase in the positive rate in recent years. However, close attention to the usage of the term, "cross-sensitization", seems to be necessary because of the increase in the indeterminate variety of allergens and their proceedings.
The suitable concentration of each allergen used for a patch test was also examined on the basis of the relationship between the concentration of allergens and the results of patch test reactions. From the results of our study, the suitable concentration of allergen used for a patch test is considered to be as follows : 10% in neomycin, bekanamycin, kanamycin, gentamicin and amikacin, and 20% in toburamycin and aminosidine.