God instructed Moses to use hyssop oil as a purifying agent. Hyssop oil has been demonstrated to contain 50% antifungal and antibacterial agents (Numbers:19:18, Psalm:51:7).
Consider also God's law of circumcision which required it to be performed specifically on the 8th day following birth (Gen:17:12, Gen:21:14, Lev:12:3, Luke:2:21). Doctors recognize that two main blood clotting factors, Vitamin K and Prothrombim, reach 110% of normal on the 8th day after birth. This aids healing and greatly reduces the possibility of infection. Obstetricians are aware that the 8th day of life is the optimum time for a circumcision, and one done earlier requires an injection of Vitamin K.
For further information:
1. Leprosy, Medic-Planet Encyclopedia.