Unaffected blood boron levels in newborn infants treated with a boric acid ointment.

No rise in the boron content of the plasma of 22 newborn infants was demonstrated following repeated daily application of a water-emulsifying ointment containing the equivalent of 3% boric acid to the napkin region. The mean plasma-boron concentration fell over 5 days from a pretreatment value of 0.49 to 0.29 mg/litre, the corresponding values in ten untreated neonates being 0.62 and 0.21 mg/litre, respectively. No statistically significant differences were found. The results confirm the safety of such ointments for application to the skin, a conclusion predicted by theoretical estimates of the maximum possible boric acid absorption following application of the ointment.