Shoo-Fly Ointment repels biting flies on dogs. It contains sunscreen to protect against the harmful effects of ultraviolet radiation and the ointment base is soothing, non-staining and cosmetically acceptable. Shoo-Fly Ointment repels biting flies on dogs. It contains sunscreen to protect against the harmful effects of ultraviolet radiation and the ointment base is soothing, non-staining and cosmetically acceptable.