Lice are small, flightless insects that live in the hair of animals. They are uncommon in dogs and cats, but when a pet does pick them up, the usual result is itching, a rough or matted coat and eggs stuck firmly to the hair. [1] This guide covers how lice are spotted and how vets deal with them.
How common are lice?
Louse infestation, called pediculosis, is uncommon in dogs and cats. [1] When a pet does have lice, vets also look for any underlying illness or other problem that may have let the lice take hold, and correct it as part of treatment. [1]
A study of free-roaming cats brought to a trap-neuter-return clinic in the central United States found the cat louse on 1.0% of cats, compared with fleas on 71.6%. [3]
Which lice affect dogs and cats?
Lice fall into two groups: biting or chewing lice, and sucking lice. [1]
- Dogs can carry two chewing lice, Trichodectes canis and Heterodoxus spiniger, and one sucking louse, Linognathus setosus, which is a rare cause of lice in dogs. [1]
- Cats are infested only by a chewing louse, the cat louse (Felicola subrostratus). [1]
Lice are highly host-specific: a dog louse stays with dogs and a cat louse with cats. They spread by direct contact with an infested animal of the same species, or through shared brushes, combs and bedding. [1]
The dog chewing louse Trichodectes canis can also carry the dog tapeworm. [1]
Signs of lice
Signs depend on how many lice there are and how long they have been there. A pet with only a few lice may show little or nothing, and some animals carry lice with no signs at all. [1]
When signs do appear, they can include: [1]
- Itching, from mild to strong
- Hair loss where the pet has scratched or chewed
- Scaling and some redness of the skin
- A rough, matted coat
- Now and then, small bumps and crusts
A heavy, long-standing infestation with the sucking louse of dogs can lead to anemia. [1]
For other causes of an itchy pet, see why is my dog so itchy? and itchy cat and overgrooming causes.
What lice and nits look like
The eggs, called nits, are cemented firmly to the hair shafts. [1] Your vet confirms lice by finding the lice or their eggs during the exam. Pressing a strip of clear sticky tape onto the coat holds the lice still so they can be seen under the microscope. [1]
Lice go through their whole life cycle on the host in about 14 to 21 days. A female lives for around a month and lays eggs every day. Off the host, lice survive only a few days. [1]
How lice are treated
Lice in dogs and cats are generally easy to treat. [1] Your vet will choose a product that kills lice and is safe for your pet’s species, age and health, and explain how to use it and whether it needs repeating.
For cats, talk to your vet first. Some parasite products made for dogs are poisonous to cats, and many cases of poisoning happen when an owner puts a dog product on a cat by mistake. [2] Never use a dog product on a cat.
Other pets in contact. All animals of the same species that live with or meet the infested pet should be treated too. [1]
Bedding and grooming tools. Wash beds, brushes and combs, since lice can spread through them. [1]
Clipping. Matted hair should be clipped before a product is applied to the skin, so your vet may suggest clipping a matted or longhaired pet. [1]
Skin damage. If scratching has broken the skin, your vet will check the sores for infection and treat any other health problems they find. See pyoderma in dogs.
Can people catch lice from pets?
This is not something to worry about. Lice are highly host-specific, so dog lice live on dogs and cat lice live on cats. [1]
When to see your vet
Book a visit if your pet has:
- Scratching, biting or rubbing at the coat
- A rough, dry or matted coat, or patches of missing hair
- Small pale specks glued to the hairs near the skin that do not wash off
- Scratch wounds or sores on the skin
FAQ
Can my dog give lice to my cat?
Lice are highly host-specific and spread between animals of the same species, so a dog’s lice are not expected to settle on a cat. [1]
Will a normal bath get rid of nits?
No. Nits are cemented firmly to the hair shafts, so a bath alone is not a treatment. Ask your vet for a product that kills lice. [1]
Why might my vet want to treat more than once?
Eggs already on the hair can hatch after the first treatment, and the life cycle takes a few weeks. Your vet will tell you if and when to repeat. [1]
Can I use my dog’s lice product on my cat?
No. Some parasite products made for dogs are poisonous to cats. Ask your vet for a product meant for cats. [2]
The bottom line
Lice are uncommon in dogs and cats. Itching and a rough or matted coat are the usual signs, though a light infestation can go unnoticed. Your vet can confirm lice, choose a safe product (especially for cats), treat the other pets of the same species and help you clean beds, brushes and combs.
This article is for general information and is not a substitute for veterinary advice. If you think your pet has lice, please see your veterinarian.
Sources
- Torres SMF. 3.13 Pediculosis (Louse infestation) – Small Animals. In: Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology/chapter/pediculosis-lice-small-animals/
- Di Pietro S, Falcone A, Arfuso F, Pennisi M, Piccione G, Giudice E. Treatment of Permethrin Toxicosis in Cats by Intravenous Lipid Emulsion. Toxics. 2022;10(4). CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC9029646/
- Thomas JE, Staubus L, Goolsby JL, Reichard MV. Ectoparasites of free-roaming domestic cats in the central United States. Vet Parasitol. 2016;228:17-22. PMID 27692321. https://pubmed.ncbi.nlm.nih.gov/27692321/