In India, neem is also used to treat viral diseases such as small-pox, chicken-pox even many medical practitioners use a paste of neem leaves, rubbed directly on the infected skin, for these conditions.

Experiments with smallpox, chicken pox and fowl-pox have shown that neem is quite effective for preventing if not for curing these conditions.  The neem extracts absorb the viruses, preventing them from spreading to unaffected cells.  Neem has also been shown to be effective against herpes virus and the viral DNA polymers of the hepatitis B virus.

Laboratory experiments have shown that neem has antibacterial characteristics as well.  For example the bacterium Staphylococcus aureus, a feared cause of food poisonings as well as of furuncles and abscesses, reacted to neem treatment.  Also, German experiments proved that a neem seed extract with ethanol is effective against the herpes viruses.