Pet parasites are small organisms that live on or in the body of a pet and feed off of their host. Two common pet parasites are LICE and fleas. LICE are tiny, wingless insects that feed on the blood of their host and can cause skin irritation and itching. Fleas are small, wingless insects that feed on the blood of their host and can cause skin irritation and itching as well as transmit diseases. Both LICE and fleas can be difficult to get rid of and require proper treatment.