Flea Ticks, fleas, and lice are the most common ectoparasites on dogs and cats, and summer and fall is the season for fleas and ticks to survive and reproduce, and they can use many diseases in your pets and even in humans themselves Flea eggs Parasitic dermatitis can cause itchy, inflamed skin and pimples on the skin. Rickettsia is transmitted by flea bites or tick bites. It's can lead to different diseases. Tick Lyme disease is considered the most common tick-borne disease in the United States. Symptoms include sudden lameness, occasionally with fever, anorexia, and lethargy. Skin Infection Meningitis is caused by numerous tick-borne viruses, and the infection results in loss of neurological function, etc. How long does it take towork on fleas? NatShield kills existing fleas on dogs within 24 hours after application. After those 24 hours, mow fleas are killed within 2 hors. Do NatShield collars for dogs expire? There is no expiration date required on the packaging by the EPA for dogs.The product should be kept in its original packaging and stored as directed on the label. What are the keyingredients Citronella oil, Cinnamon oil, Garlic oil, Thyme, Lemongrass oil, Other Ingredients Water Resistance Level Waterpoof