Hair Loss in Dogs (Alopecia)

What Causes Hair Loss in Dogs?

Common underlying causes include allergic skin disease, infections, parasites, hormonal conditions and disorders affecting the hair follicle. Hair loss (Alopecia) can result from several different disease processes affecting the skin, hair follicle or wider systemic health. In many cases, the underlying cause can be identified by assessing the pattern, distribution and associated clinical signs.

Hair loss is best understood by considering the potential underlying causes and contributing factors:

While hair loss itself is often the most noticeable sign, it is typically a symptom rather than a primary diagnosis. Identifying the underlying cause is essential for effective management.

Signs Associated with Hair Loss in Dogs

Hair loss may present in different ways depending on the underlying cause. It may be localised or widespread, and may develop suddenly or progress gradually over time.

• Patchy or symmetrical hair loss
• Thinning of the coat or failure of hair to regrow
• Red, inflamed or irritated skin
• Scaling, crusting or changes in skin texture
• Darkening or thickening of the skin in chronic cases
• Licking, scratching or chewing, particularly in itchy conditions
• Recurrent skin or ear infections
• Changes in coat quality, including dryness or dullness

The pattern and distribution of hair loss often provide important clues. For example, symmetrical hair loss without itching may suggest a hormonal cause, while patchy hair loss with inflammation may indicate allergy or infection.

Why Hair Loss Can Become Ongoing or Recurrent

Hair loss may persist or recur when the underlying cause is not identified or adequately managed, or when secondary factors continue to affect the skin and hair cycle. In some cases, repeated inflammation, infection or trauma can disrupt the normal hair growth cycle, preventing regrowth.

This can lead to a cycle where:

• An underlying condition affects the skin or hair follicle
• Inflammation or infection develops
• Hair is lost due to damage or disruption of the hair cycle
• The skin remains abnormal, preventing normal regrowth
• Secondary factors such as infection or trauma further delay recovery

In chronic cases, the skin may become thickened, pigmented or scarred, making hair regrowth more difficult even once the underlying cause is controlled.

How We Diagnose the Causes of Hair Loss in Dogs

Hair loss can have many different causes, so a systematic and structured approach is required to to identify the underlying condition and guide targeted treatment. Where referral is recommended, your dog’s assessment begins with a dermatology consultation, where our clinician reviews their history and previous treatments, and performs a thorough examination to assess the type, distribution and progression of hair loss and associated skin changes.

From here, our clinicians tailor a targeted diagnostic approach to your dog’s individual presentation.

A tailored diagnostic approach may include:

• Cytology and Fine-Needle Aspirates – used to identify infection or inflammation that may be contributing to hair loss. 
• Hormone Disorder Testing – used in selected cases where an endocrine condition is suspected as an underlying cause. 
• Elimination Diet Trials – used where a cutaneous adverse food reaction is suspected. 
• Airborne Environmental Allergy Testing – used in selected cases where environmental allergy is suspected as an underlying cause of recurrent skin disease and infection, helping guide allergen-specific immunotherapy (ASIT). 
• Biopsy and Dermatopathology – recommended in selected cases to assess the hair follicle and support diagnosis of more complex or unusual conditions. 
• Skin scrapings and parasite testing – used to rule out mites and other parasitic causes
• Assessment of flea exposure and response to effective flea control – particularly where flea allergy dermatitis is suspected

Each step helps build a complete clinical picture, ensuring that treatment is based on an accurate diagnosis.

How Hair Loss in Dogs Is Managed

Management depends on the underlying cause, the severity and duration of hair loss, and your dog’s individual needs. Effective treatment focuses on addressing the primary condition, supporting skin health and allowing normal hair regrowth.

Depending on the diagnosis, treatment may include:

• Treatment of underlying allergy or skin disease
• Management of bacterial or yeast infections where present
• Treatment of hormonal (endocrine) conditions
• Parasite control, where relevant
• Dietary management where a food-related trigger is identified
• Medications to reduce inflammation and itching (pruritus) where present
• Supportive therapies to improve skin and coat health

For many dogs, hair regrowth occurs once the underlying condition is controlled, although this may take time depending on the hair growth cycle and severity of disease.

The goal is not simply to improve coat appearance, but to restore skin health, support normal hair growth, and achieve long-term stability.

Related Conditions

Dog Allergies

Skin Infections in Dogs

Parasites in Dogs

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