I assume CROFTERLOON that you have made a mistake on the product name, as CLIK only stops blowfly. Lice does not affect only one sheep in a group ,just different levels of infection and balding over a large area is not a common symptom. FOOBAR since i stopped dipping i have had lice every winter , it seems that a few lice survive treatment and the summer to increase in the autumn, always starts in the lambs.