PET PESTS are small, parasitic creatures that can cause discomfort and irritation to both humans and animals. Fleas are small, wingless insects that feed on the blood of their hosts and can cause itching and skin irritation. LICE are small, wingless parasites that feed on the blood of their hosts and can cause itching and skin irritation. Both fleas and LICE can be difficult to get rid of and can spread quickly if not treated properly.