Is skin preparation necessary before insulin injection?

The effect of routine skin preparation on skin bacterial flora was measured in thirteen insulin-dependent diabetic patients. 5 seconds of skin cleansing of sites on the leg, arm, and abdomen with 70% isopropyl alcohol reduced bacterial counts by 82-91%. During a 3-5 month observation period the subjects omitted skin preparation before insulin injection every other week. More than 1700 insulin injections were given without skin preparation. No signs of local or systemic infection were observed. These results indicate that routine skin preparation with alcohol before insulin injection markedly reduces skin bacterial-counts but may not be necessary to prevent infection at the injection sites.