Dog Hair Loss — Causes, Patterns & What It Means
Hair loss (alopecia) in dogs can be localized or widespread, and the pattern often indicates the underlying cause. While some shedding is normal, bald patches or excessive hair loss usually signals allergies, infections, parasites, or hormonal imbalances that may require treatment.
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Common Causes
Allergies (Environmental or Food)
Schedule Vet VisitThe most common cause of hair loss. Dogs scratch and lick itchy areas, causing fur loss. Often affects the paws, ears, belly, and rear. May be seasonal (environmental) or year-round (food).
Flea Allergy Dermatitis
Schedule Vet VisitAllergic reaction to flea saliva causes intense itching and hair loss, especially at the base of the tail, rear legs, and lower back. Even one flea can trigger a reaction.
Mange (Mites)
See Vet ImmediatelyDemodectic mange causes patchy hair loss, often on the face. Sarcoptic mange (scabies) causes intense itching and widespread hair loss. Both require veterinary treatment.
Ringworm (Fungal Infection)
Schedule Vet VisitDespite the name, it's a fungus, not a worm. Causes circular patches of hair loss with scaly, crusty edges. Highly contagious to other pets and humans.
Hypothyroidism
Schedule Vet VisitUnderactive thyroid causes symmetrical hair loss on the body (not head or legs), dull coat, weight gain, and lethargy. Common in middle-aged dogs.
Cushing's Disease
Schedule Vet VisitExcess cortisol causes symmetrical hair loss on the body, thin skin, pot-bellied appearance, and increased thirst/urination. Usually in older dogs.
Bacterial or Yeast Infections
Schedule Vet VisitSecondary infections from scratching cause hair loss, redness, odor, and sometimes greasy or flaky skin. Often occurs alongside allergies.
Stress or Anxiety
Monitor at HomeCompulsive licking (psychogenic alopecia) causes hair loss in areas the dog can reach, typically the legs or flanks. The skin underneath usually looks normal.
How to Photograph for Best AI Analysis
Getting a clear photo helps our AI provide more accurate insights. Follow these tips:
- Photograph the bald area clearly, showing the skin underneath
- Take a wider shot showing the pattern and location of hair loss
- Note if the hair loss is symmetrical (same on both sides)
- Show any redness, scaling, or unusual skin appearance
- Photograph the edges of the bald area — are they sharp or gradual?
- If there are multiple areas, photograph each one
When to See a Veterinarian
Contact your veterinarian if you notice any of the following:
- •Hair loss is accompanied by red, irritated, or scaly skin
- •Your dog is intensely itchy or scratching constantly
- •Circular patches with crusty edges (possible ringworm)
- •Hair loss is symmetrical on both sides of the body
- •Other symptoms like weight changes, increased thirst, or lethargy
- •You see any sores, bumps, or signs of infection
- •Hair loss is spreading or getting worse
- •The skin has an unusual odor or greasy texture
How PetSensAI Can Help
PetSensAI's skin and coat scanner can help document hair loss patterns and skin condition. Our AI analyzes photos to identify characteristics that may indicate the underlying cause — whether it's a skin infection, parasites, allergies, or something that needs further testing.
Related Symptoms
Sources
- Merck Veterinary Manual — Hair Loss (Alopecia) in Dogs
- Merck Veterinary Manual — Dermatitis in Dogs
About the Author
PetSensAI Editorial Team
Pet Health Content
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Last updated: 2025-01-09