I'v bought 2 guinea pigs..male n a female..dey r 6mnths old..dey hv got ol over dier body white lice.?

N d female hv lost mny hairs..as d male jst keeps on bitting her hairs..dey are active..bt mny lices r around dier body specially near ears n eyes..i gv dem grass 2 eat..d doc haz recommended betnesol oral drops..plzz help.,...i rely love dem..