Lice in Dogs and Cats: Signs, Treatment and How To Get Rid of Them

By Dr Duncan Houston

Seeing white specks fixed to your pet’s hair or small insects crawling through the coat can be alarming. Fortunately, lice infestations in dogs and cats are usually straightforward to treat once the parasite has been correctly identified.

The bigger challenge is determining whether the pet genuinely has lice. Dandruff, fleas, Cheyletiella mites, skin infection and allergic skin disease can all cause itching and flaky material in the coat.

Lice are uncommon in healthy pets receiving regular parasite prevention. When they occur heavily, particularly in an older cat, a very young puppy or a debilitated animal, the infestation may also be a clue that an underlying health or grooming problem needs attention. (Companion Animal Parasite Council)

Quick Answer

Dogs and cats can develop host-specific lice that live in the coat, crawl rather than jump and glue their eggs, called nits, firmly to individual hairs.

Treatment usually involves a species-appropriate veterinary ectoparasiticide, simultaneous treatment of exposed animals of the same species and at least one follow-up step to kill lice hatching from surviving eggs. Pet lice do not establish infestations on people, and human head lice do not live on dogs or cats. (Companion Animal Parasite Council)

Lice in Pets at a Glance

Question	Practical answer
What do lice look like?	Small yellow, tan or grey insects approximately 1 to 2.5 mm long
Do lice jump?	No. They crawl through the coat and cling to hairs
What are nits?	Louse eggs glued firmly to individual hair shafts
Can dogs catch cat lice?	No. Canine and feline lice are strongly host-specific
Can people catch lice from pets?	No. Pet lice do not establish human infestations
How do lice spread?	Mainly through direct contact, but also through contaminated brushes, bedding and grooming equipment
Do all lice cause anaemia?	No. Anaemia is mainly a concern with heavy infestations of the canine sucking louse
Is one treatment enough?	Sometimes, but many plans require repeat treatment because nits may survive
Does the whole house need insecticide treatment?	Usually not. Cleaning bedding and grooming tools is generally sufficient
When is it urgent?	Pale gums, weakness, collapse, severe skin infection or insecticide toxicity

This summary reflects the species, life cycle, transmission and clinical effects described by CAPC and ESCCAP. (Companion Animal Parasite Council)

What Are Lice?

Lice are small, wingless insects that spend almost their entire life on an animal’s skin and hair.

They have six legs and a flattened body. Their claws and mouthparts help them cling to hairs, which is why they do not fall from the coat as easily as dandruff.

There are two functional groups:

• Chewing lice, which feed on skin debris, secretions and superficial tissue

• Sucking lice, which pierce the skin and feed on blood and tissue fluid

Adult females lay several eggs each day. These eggs are cemented near the base of individual hairs and normally hatch within one to two weeks. The nymphs resemble smaller adult lice and mature over another two to three weeks. (Companion Animal Parasite Council)

Which Lice Affect Dogs?

The main canine species are:

Trichodectes canis

This is a chewing louse found on dogs and wild canids. It feeds on skin debris and may cause itching, coat damage and dermatitis when present in large numbers.

It can also act as an intermediate host for the tapeworm Dipylidium caninum. A dog may acquire this tapeworm by swallowing an infected louse while grooming. (Companion Animal Parasite Council)

Linognathus setosus

This is a blood-sucking canine louse. Heavy infestations may cause clinically significant blood loss and anaemia, particularly in puppies, small dogs, immunosuppressed dogs or already debilitated animals. (Companion Animal Parasite Council)

Heterodoxus spiniger

This is another canine chewing louse found mainly in warmer and tropical regions. It is less commonly discussed in general pet-care articles but may be locally relevant in suitable climates. (Companion Animal Parasite Council)

Which Lice Affect Cats?

Cats are affected mainly by:

Felicola subrostratus

This is a chewing louse. It has a distinctive triangular head and feeds on superficial skin material rather than blood.

Heavy infestations are seen most often in older, sick, debilitated, long-haired, feral or poorly grooming cats. The presence of large numbers of lice in a household cat should prompt consideration of dental pain, arthritis, obesity, chronic disease or another reason the cat is no longer grooming normally. (Companion Animal Parasite Council)

Cats do not have the blood-sucking species described in dogs, so severe anaemia is not a typical consequence of ordinary feline lice infestation.

Lice, Fleas, Dandruff or Mites?

Finding	Lice and nits	Fleas	Dandruff	Mites
Movement	Lice crawl through the hair	Fleas move quickly and may jump	Does not move	Most mites are too small to see clearly
Colour	Yellow, tan, grey or reddish after feeding	Usually dark brown	White or pale flakes	Variable
Attachment	Nits are firmly glued to hairs	Flea dirt and eggs are not cemented to hairs	Flakes brush or shake away	May require skin scrapings or microscopy
Common signs	Scratching, rough coat, hair loss	Itching, flea dirt, flea allergy	Scaling with many possible causes	Itching, crusting, hair loss or “walking dandruff”
Can it affect humans?	Pet lice do not establish on people	Fleas may bite people	No	Some mites can temporarily affect people

Lice are diagnosed by finding an adult insect or firmly attached nit. Mites and several other itchy skin conditions may require coat examination, adhesive-tape testing, skin scrapings, cytology or other veterinary testing.

How Can You Tell Nits From Dandruff?

Nits are glued to individual hairs and usually remain attached when the hair is moved between your fingers.

Dandruff consists of loose skin flakes. It usually slides along the hair or falls away when the coat is brushed or shaken.

A magnifying glass, bright light and fine-toothed flea comb may help, but uncertain material should be placed on clear tape or in a sealed container and taken to your veterinarian.

How Do Dogs and Cats Get Lice?

Transmission most commonly occurs through prolonged direct contact with an infested animal of the same species.

Risk is higher in:

• Shelters and rescue facilities

• Crowded kennels or catteries

• Breeding establishments

• Stray or feral populations

• Households introducing an untreated rescue animal

• Animals sharing brushes, combs, clippers or bedding

• Young, old or debilitated pets

• Pets not receiving regular ectoparasite prevention

Eggs attached to shed hairs may occasionally spread through grooming tools, bedding, carriers or other contaminated equipment. Dogs do not ordinarily acquire feline lice, and cats do not ordinarily acquire canine lice. (Companion Animal Parasite Council)

How Long Can Lice Survive Without a Pet?

Most canine and feline lice survive only approximately three to seven days once separated from their host.

This is very different from fleas, whose immature stages may persist throughout the environment. Environmental cleaning remains useful for lice, but controlling the infestation on the animal is the most important part of treatment. (Companion Animal Parasite Council)

What Are the Signs of Lice?

Mild Infestations

A pet may have:

• A slightly rough or dry-looking coat

• Visible nits attached to hairs

• Occasional scratching

• Small numbers of slowly moving insects

• No significant redness or hair loss

Some cats carry lice with remarkably little visible discomfort.

Established Infestations

More obvious disease may cause:

• Persistent scratching

• Biting or rubbing the skin

• Restlessness

• Poor sleep

• Hair breakage

• Patchy hair loss

• A rough, matted or scruffy coat

• Scaling

• Crusts

• Red or inflamed skin

• Secondary bacterial infection

Chewing lice are commonly found around the head, neck and tail, and may gather near body openings or damaged skin where moisture is available. (Companion Animal Parasite Council)

Signs of Sucking Lice in Dogs

Dogs with a heavy Linognathus setosus infestation may develop:

• Pale gums

• Weakness

• Reduced stamina

• Rapid heart rate

• Poor growth in puppies

• Lethargy

• Collapse in extreme cases

These signs are caused by blood loss and require prompt veterinary assessment rather than another home shampoo. (Companion Animal Parasite Council)

Could Lice Cause Tapeworms?

The canine chewing louse Trichodectes canis can carry the larval stage of Dipylidium caninum.

A dog becomes infected by swallowing an infected louse during grooming. Owners may later notice mobile, rice-like tapeworm segments around the anus, in faeces or on bedding.

Treating the tapeworm without controlling the lice allows reinfection to occur. (Companion Animal Parasite Council)

How Worried Should You Be?

Low Risk

Your pet has:

• A few visible lice or nits

• Mild scratching

• Normal appetite and activity

• Healthy pink gums

• No open wounds

• No significant hair loss

What it may mean: An uncomplicated louse infestation is likely.

What to do: Separate the affected animal from same-species contacts, arrange veterinary treatment within the next few days and clean shared grooming equipment.

Moderate Concern

Your pet has:

• Frequent scratching

• Patchy hair loss

• A rough or matted coat

• Crusts or mild skin inflammation

• Multiple affected pets

• Persistent infestation despite one treatment

What it may mean: The infestation is established, another animal is maintaining transmission or the treatment has not covered newly hatched nymphs.

What to do: Arrange a veterinary examination and treatment review. All exposed animals of the same species may need simultaneous treatment.

High Concern

Your pet has:

• Pale gums

• Marked weakness

• Significant weight loss

• Extensive skin wounds

• Pus, odour or painful skin

• A very heavy visible infestation

• Poor growth in a puppy or kitten

• An underlying chronic illness

What it may mean: Anaemia, secondary infection or significant underlying disease may be present.

What to do: Seek same-day veterinary care.

Critical

Your pet has:

• Collapse

• Severe weakness

• White or grey gums

• Difficulty breathing

• Uncontrolled bleeding

• Tremors, drooling, twitching or seizures after parasite treatment

• Severe loss of responsiveness

What it may mean: Severe anaemia, an adverse drug reaction or insecticide poisoning may be present.

What to do: Attend an emergency veterinary hospital immediately.

When Is This an Emergency?

Lice themselves rarely create an immediate emergency. Their complications or an incorrect treatment can.

Seek urgent veterinary care when your pet develops:

• Very pale or white gums

• Collapse or inability to stand

• Severe weakness

• Rapid or laboured breathing

• A painful, rapidly spreading skin infection

• Deep bleeding wounds from scratching

• Complete food refusal in a puppy or kitten

• Tremors, muscle twitching or seizures

• Severe drooling or vomiting after a parasite product

• Marked behavioural change after treatment

A cat showing tremors, twitching, drooling, incoordination or seizures after contact with a dog flea or tick product may have permethrin toxicity. Remove further access and contact an emergency veterinarian immediately. Do not wait to see whether the signs settle. (Merck Veterinary Manual)

What Else Can Look Like Lice?

Important alternatives include:

• Fleas

• Cheyletiella mites

• Sarcoptic mange in dogs

• Notoedric mange in cats

• Demodicosis

• Ringworm

• Bacterial folliculitis

• Yeast dermatitis

• Flea allergy

• Environmental or food-related allergic skin disease

• Seborrhoea or excessive scaling

• Poor grooming caused by arthritis, obesity, dental disease or chronic illness

A heavily scaling coat should not automatically be treated for lice unless adult insects or attached eggs are actually identified. (Merck Veterinary Manual)

What To Do Right Now

1. Separate the Affected Pet

Prevent close contact with other dogs if a dog is affected, or other cats if a cat is affected.

Because the lice are host-specific, a dog with canine lice is unlikely to infest a cat. The animals may still share fleas, mites or another skin condition, so every pet should be checked.

2. Inspect the Coat in Bright Light

Part the hair and examine:

• Around the ears

• Neck and shoulders

• Along the back

• Tail base

• Around the anus

• Beneath matted hair

• Any itchy or damaged area

Look for slowly moving insects and eggs firmly attached to hairs. (Merck Veterinary Manual)

3. Photograph or Collect a Sample

Place suspected lice or affected hairs:

• On clear adhesive tape

• In a clean sealed container

• Against a contrasting background for photographs

Do not spray the sample with insecticide before taking it to the clinic.

4. Do Not Apply Random Flea Products

The correct product depends on:

• Dog or cat

• Age

• Body weight

• Pregnancy or nursing status

• General health

• Other medications

• Country-specific licensing

• The active ingredient already used

A flea product is not automatically suitable for lice, and a dog product is not automatically safe for a cat.

5. Do Not Use Human Head-Lice Products

Human shampoos and household insecticides are not formulated or tested for routine use on dogs and cats.

They may be ineffective, irritating or toxic.

6. Check the Gums

Healthy gums should normally look pink.

Pale, white or grey gums in an infested puppy or dog raise concern for anaemia and require prompt veterinary assessment.

7. Wash Shared Equipment

Until treatment is completed, do not share:

• Brushes

• Combs

• Clippers

• Collars

• Coats

• Beds

• Blankets

• Carriers

How Are Lice Diagnosed?

Diagnosis is usually straightforward when adult lice or attached nits can be seen in the coat.

The veterinarian may:

1. Examine the entire coat under bright light

2. Use a flea comb

3. Remove hairs carrying nits

4. Examine the parasite under a microscope

5. Look for fleas, mites or fungal disease

6. Assess for anaemia or secondary infection

7. Investigate why an older or debilitated animal is no longer grooming normally

Chewing and sucking lice can often be distinguished by head shape. Chewing lice have a broad head, while sucking lice have a narrower head designed for piercing the skin. (Companion Animal Parasite Council)

Are Blood Tests Needed?

Not for every infestation.

Blood testing may be appropriate when the pet has:

• Pale gums

• Weakness

• Weight loss

• Chronic illness

• Poor growth

• Severe skin disease

• Recurrent or unusually heavy infestation

A heavy burden in an apparently well-kept adult pet may justify looking for an underlying condition affecting immunity, mobility or grooming.

How Are Lice Treated?

Treatment requires:

1. Killing the live lice

2. Dealing with newly hatched nymphs

3. Treating exposed animals

4. Cleaning bedding and equipment

5. Managing skin damage or anaemia

6. Preventing reinfestation

Veterinary Parasite Products

Several veterinary ectoparasiticides can kill canine and feline lice. Depending on the product, country and species, active ingredients may include:

• Fipronil

• Imidacloprid

• Selamectin

• Selected isoxazolines

• Selected dog-only pyrethroid products

Product labels and licensed claims vary. The veterinarian should select the safest option for the individual animal and confirm whether repeat treatment is required. (Companion Animal Parasite Council)

Never Use Dog Permethrin Products on Cats

Permethrin and several related concentrated dog ectoparasiticides can cause severe or fatal poisoning in cats.

Cats may be exposed through:

• Direct application of a dog product

• Licking a recently treated dog

• Sleeping against a recently treated dog

• Contact with contaminated bedding

Keep cats separated from treated dogs for the full period stated on the label. Seek immediate veterinary treatment if exposure occurs or neurological signs develop. (APVMA)

Does Treatment Need To Be Repeated?

Often, yes.

Many treatments kill adult lice and nymphs more reliably than eggs. Nits may hatch one to two weeks after the first application.

Depending on the product, the veterinarian may recommend:

• A repeat treatment after approximately one week

• A longer-acting product that kills newly hatched lice

• Another product-specific schedule

Do not automatically give three or four doses every two weeks. Follow the selected product’s instructions and the veterinary treatment plan. (Companion Animal Parasite Council)

Should Every Pet Be Treated?

All exposed animals of the affected species should be examined, and simultaneous treatment is commonly recommended.

For example:

• If one dog has canine lice, assess and usually treat the other dogs.

• If one cat has feline lice, assess and usually treat the other cats.

• Do not apply one species’ medication to another species.

Treating only the visibly affected animal may allow an apparently normal carrier to restart the infestation.

Does the Coat Need To Be Shaved?

Not routinely.

Clipping may help when:

• The coat is severely matted

• Lice and nits cannot be reached

• Topical medication cannot contact the skin properly

• Skin infection is hidden beneath dense hair

• The pet cannot groom

Clipping should be performed carefully because inflamed skin is easily damaged. Severe infestations may require professional grooming or sedation rather than a home haircut with increasingly optimistic kitchen scissors. (Merck Veterinary Manual)

Are Antibiotics Needed?

Not for the lice themselves.

Antibiotics may be needed when repeated scratching has produced a confirmed or strongly suspected bacterial skin infection.

Most uncomplicated infestations improve after the parasites are eliminated and the skin is kept clean. Antibiotics should not replace adequate parasite treatment.

What if the Dog Also Has Tapeworms?

A dog with Trichodectes canis exposure may need assessment for Dipylidium caninum, particularly if rice-like segments are visible.

Tapeworm treatment commonly requires praziquantel or another veterinarian-selected cestocide, while simultaneous control of the louse infestation prevents reinfection. (Companion Animal Parasite Council)

How Should the Home Be Cleaned?

Lice do not establish large household populations in the way fleas can.

A sensible cleaning plan includes:

• Washing bedding on a hot cycle when the material allows

• Drying bedding thoroughly using heat

• Cleaning brushes, combs and clippers

• Vacuuming resting areas

• Cleaning carriers

• Removing shed hair

• Replacing heavily contaminated or difficult-to-clean bedding

• Keeping treated animals in a clean living space

Hot, dry conditions accelerate the death of lice and eggs away from the host. (Companion Animal Parasite Council)

Are Foggers or House Sprays Needed?

Usually not.

Because lice spend their entire life cycle on the animal and survive only a few days away from the host, routine household foggers generally add little to a correctly managed treatment plan.

Environmental insecticides may expose pets and people unnecessarily. Use them only when specifically recommended for the identified parasite and living environment.

How Long Does It Take To Get Rid of Lice?

Live lice should begin dying after an effective treatment, but firmly attached nits may remain visible for some time.

The coat may take several weeks to look normal because:

• Nits remain attached until removed or the hair grows out

• Damaged hairs need to regrow

• Skin inflammation takes time to settle

• Secondary infection may need treatment

• Newly hatched nymphs must be eliminated

Recheck the pet approximately one to two weeks after treatment, or at the interval recommended by your veterinarian.

If live lice remain, reassess:

• Product choice

• Dose

• Application technique

• Bathing after treatment

• Untreated contacts

• Reinfestation from equipment

• Whether the organism was correctly identified

Common Mistakes With Pet Lice

Treating Dandruff Without Confirming Lice

White material in the coat is not automatically a nit. Nits are firmly attached to individual hairs.

Treating Only One Dog or Cat

An untreated same-species contact may maintain the infestation even when they are not visibly itchy.

Using a Dog Product on a Cat

This can cause life-threatening poisoning, particularly with concentrated permethrin products.

Skipping the Follow-Up Treatment

Surviving eggs may hatch after the first application and restart the infestation.

Using Household Foggers as the Main Treatment

The animal is the primary habitat. Treating the host correctly is more important than filling the home with insecticide.

Ignoring Pale Gums

A puppy with heavy sucking lice may become anaemic. Weakness or pale gums requires more than parasite shampoo.

Ignoring the Reason the Pet Became Infested

Heavy lice in an older cat or debilitated animal may indicate reduced grooming, chronic pain, malnutrition or systemic illness.

How Can Lice Be Prevented?

Examine New Animals Before Introduction

Check newly adopted, rescued or fostered pets before they mix with resident animals.

Pay particular attention to:

• Rough coat

• Excessive scratching

• Nits attached to hairs

• Matted fur

• Hair loss

• Poor body condition

Maintain Appropriate Parasite Prevention

Several regular flea and tick preventives also control lice, but efficacy and label claims vary.

Ask your veterinarian whether the product currently used covers the lice relevant to your pet and region. (Companion Animal Parasite Council)

Do Not Share Grooming Equipment

Avoid sharing brushes, combs, clippers and bedding between unfamiliar animals unless they have been cleaned.

Support Normal Grooming

Investigate why a cat or dog has stopped grooming effectively.

Common contributors include:

• Arthritis

• Obesity

• Dental pain

• Neurological disease

• Severe matting

• Chronic illness

• General weakness

Reduce Crowding

Adequate space, hygiene and prompt examination of itchy animals are particularly important in shelters, boarding facilities, rescues and breeding environments.

Frequently Asked Questions

Can humans catch lice from dogs or cats?

No. Canine and feline lice are highly host-specific and do not establish infestations on people. Human head lice also do not live on dogs or cats. (Companion Animal Parasite Council)

Can dogs catch lice from cats?

No. Dogs and cats have different louse species. Direct contact between them will not ordinarily transfer a sustainable infestation.

Can lice live in carpets and furniture?

Only briefly. Most pet lice survive approximately three to seven days away from the host. Vacuuming, laundering bedding and cleaning grooming tools are usually sufficient. (Companion Animal Parasite Council)

Can one treatment eliminate lice?

Sometimes, particularly with a product that has sufficient residual activity. However, nits may survive and hatch later, so a product-specific repeat treatment or recheck is commonly needed. (Companion Animal Parasite Council)

Should I shave my pet?

Not unless matting or coat density prevents effective treatment. Most pets can be treated without shaving, although clipping may help in severe or neglected infestations.

Final Thoughts

Lice are uncommon in well-cared-for dogs and cats, but they remain an important cause of itching and coat damage in young, old, debilitated and crowded animals.

The most important points are:

1. Dogs and cats have different, host-specific lice.

2. Pet lice do not establish infestations on people.

3. Lice crawl and do not jump.

4. Nits are glued firmly to individual hairs.

5. The full life cycle takes approximately four to six weeks.

6. Lice survive only a few days away from the host.

7. Heavy canine sucking-louse infestations can cause anaemia.

8. The canine chewing louse can transmit Dipylidium caninum.

9. Diagnosis requires finding an adult louse or attached nit.

10. Several veterinary flea-control products also kill lice.

11. Product licensing and safety vary by species and country.

12. Dog permethrin products must never be applied to cats.

13. Exposed animals of the same species should be assessed and usually treated together.

14. Repeat treatment may be required because eggs can survive the first application.

15. Bedding and grooming tools should be cleaned, but household foggers are rarely necessary.

16. Severe infestation in an older or debilitated animal may indicate an underlying health problem.

17. Pale gums, collapse or neurological signs after treatment require urgent veterinary care.

The mistake that causes the greatest trouble is treating the visible lice while overlooking their eggs, exposed housemates and the reason the pet became heavily infested in the first place.

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ASK A VET™ can help you review photographs of suspected lice or nits, check whether a parasite product is appropriate for your pet’s species and weight, and organise follow-up treatment reminders while you work directly with your veterinarian. A pet with pale gums, severe weakness, breathing difficulty, extensive infected skin or tremors after a parasite product still requires immediate hands-on veterinary care.