The 12 Most Common Causes of Hair Loss in Dogs

Your Retriever is losing clumps of hair on the sofa. Or you discover a coin-sized bald spot on your mixed-breed dog’s ear. Hair loss in dogs is never just a cosmetic problem, the skin shows you what is going on inside the body.

Veterinarians call medical hair loss alopecia. It can occur locally or over large areas. Sometimes the area itches terribly, sometimes it looks completely normal. The cause determines the urgency.

Why is my dog scratching its hair off?

Itching is the most common reason for self-inflicted hair loss. The dog scratches, licks or bites at one spot until the hair disappears.

The triggers: fleas leave tiny black crumbs in the coat, flea dirt. Food allergies often show up on ears and paws first. Environmental allergies (pollen, house dust mites) intensify seasonally.

Bacterial skin infections smell strong and leave yellowish crusts. Fungal infections spread in a circular pattern, hence the name “ringworm”.

In case of persistent scratching: elimination diet over 8-12 weeks with a protein source your dog has never eaten before. In parallel, flea treatment for all animals in the household plus the environment.

Which parasites cause bald spots?

Demodex mites normally live harmlessly in the hair follicles. Under stress or with a weak immune system, they multiply explosively.

Puppies often develop local Demodex patches around the eyes, usually harmless and self-healing. Adult dogs with generalised demodicosis have an underlying problem: immunodeficiency, hormonal disorder or cancer.

Sarcoptes mites (scabies) are highly contagious and cause extreme itching. The mites burrow tunnels into the skin, typical signs are crusted ear margins.

Modern spot-on preparations work against most mite species. With Sarcoptes, all contact animals must be treated simultaneously.

Can hormones trigger hair loss?

Hypothyroidism is the most common hormonal cause of hair loss in dogs aged 4 years and older. The coat becomes thin, dull and falls out symmetrically, often on the tail and hind legs first.

Cushing’s syndrome (overproduction of cortisol) shows as a “rat tail”, where the tail loses all hair except at the tip. This is accompanied by ravenous hunger, increased drinking and a distended belly.

Neutering can lead to diffuse hair loss in bitches. Affected breeds are often Spaniels, Setters and Dachshunds. The oestrogen deficiency changes the hair structure.

Diagnosis is made via blood tests. Thyroid values show T4 and TSH; if Cushing’s is suspected, a dexamethasone suppression test is necessary.

How do I recognise deficiencies in the coat?

Zinc deficiency shows as scaly, crusted areas around the mouth and eyes. Nordic breeds such as Huskies often have a genetically determined zinc metabolism defect.

Protein deficiency leads to dull, brittle coat. The hairs break off rather than falling out. Usually an intestinal disease is underlying, preventing nutrient absorption.

Omega-3 fatty acid deficiency makes the coat dry and scaly. Home-cooked rations without fish oil supplementation are particularly affected.

A high-quality complete diet prevents deficiencies. Dietary supplements only after veterinary diagnosis; overdosing does more harm than good.

Can stress lead to hair loss?

Lick dermatitis arises from compulsive licking at one body part. Border Collies, German Shepherds and Dobermans tend to do this when bored or suffering from separation anxiety.

The area becomes bald from licking, gets inflamed and itches, creating a vicious circle. Without addressing the cause, the wound never heals.

Moving, a new family member or changed routines can trigger stress. Some dogs react with self-harming behaviour.

Bitter spray stops the licking short-term. Long-term help only comes from: more mental and physical stimulation, clear routines and in severe cases behavioural therapy.

How do I recognise skin infections?

Bacterial folliculitis shows as small pustules that burst and crust over. The bald spots often have a reddish edge.

Ringworm (dermatophytes) forms circular, scaly patches. Some fungal species fluoresce green under a Wood’s lamp, but not all.

Yeast infections (Malassezia) smell strongly of rancid fat and leave brown deposits. Droopy-eared breeds are particularly affected.

The diagnosis is confirmed by a skin scraping or fungal culture. Antibiotics for bacteria, antifungals for fungi, but never without prior pathogen identification.

Can medications cause hair loss?

Chemotherapeutic agents cause hair loss less frequently in dogs than in humans. Poodles and other breeds with continuous hair growth are more likely to be affected.

Long-term corticosteroid therapy makes the coat thin and brittle. The skin becomes parchment-like and tears at the slightest injury.

Anticonvulsants (epilepsy medications) can trigger diffuse hair loss. The effect is usually reversible after discontinuation.

In cases of medication-induced hair loss, never discontinue treatment independently. The vet can suggest alternative active ingredients or adjusted dosages.

What are pressure sores and how do they develop?

Lying calluses develop in large, heavy dogs on their elbows and hocks. Constant pressure on hard floors causes the hair to disappear.

Great Danes, Rottweilers, and other Molossers are particularly affected. Without treatment, open wounds that heal poorly develop.

Orthopaedic dog beds with memory foam distribute weight evenly. Existing lying calluses require padding and anti-inflammatory ointments.

Deep wounds require surgical treatment. Healing takes weeks to months.

Are there breed-specific forms of alopecia?

Seasonal flank alopecia affects Bulldogs, Airedales, and Schnauzers between November and March. The hair on the flanks falls out symmetrically and regrows in spring.

Dermatomyositis in Collies and Shelties appears as scaly, hairless patches on the face. The condition is genetically determined and incurable.

Colour-dilution alopecia affects blue and fawn Dobermans from their first year of life. The diluted pigments make the hair brittle.

Selective breeding could reduce these problems. Affected animals should not be used for breeding.

How dangerous are skin tumours?

Basal cell carcinomas grow slowly and remain locally confined. They look like wart-like, hairless nodules, usually harmless but bothersome.

Mast cell tumours can occur anywhere and metastasise rapidly. Any new swelling should be investigated by a vet.

Squamous cell carcinomas often develop from chronic wounds or areas heavily exposed to the sun. White dogs with thin coats are at risk.

The decision for or against surgery depends on age, health status, and tumour type. A biopsy provides certainty.

Can poisoning trigger hair loss?

Rat poison (coumarins) leads to hair loss and skin bleeding with chronic ingestion. The anticoagulant effect often does not show until days later.

Thallium from ant poison or rat poison causes complete hair loss within 2–3 weeks. The poisoning is often fatal.

Selenium overdose through low-quality dietary supplements makes the hair brittle and causes it to fall out in clumps.

In case of suspected poisoning, go to the vet immediately. Only induce vomiting if the dog is conscious and has not ingested caustic substances.