Hair Loss (Alopecia) in Dogs

Key Takeaways

Hair loss, or alopecia, is characterized by hair loss leading to bald patches and places in the coat that are abnormally sparse. 

• Types of hair loss are characterized using the nature of the hair loss (symmetric or asymmetric), the presence of pruritus (itching), and the age of onset

• Alopecia can have a number of causes in dogs including allergies, dermatitis, cancers, infections, and physical injury to the skin

• Diagnostics involve testing for bacterial, fungal, and parasitic infection, skin scrapings and biopsies, blood and urine analysis, and therapeutic trials

• Once the cause is identified, the treatment varies but may include antibiotics/antifungals, specific medications, topical treatments, and immunotherapy

A Closer Look: What is Hair Loss in Dogs?

Hair loss in dogs can vary in severity and can be separated into different variations using a few classifications;

Acquired vs. congenital: Congenital forms of hair loss are characterized by symmetric hair loss or a loss in a single area These conditions are present from birth. Acquired conditions can vary in severity and pattern (symmetric, asymmetric, patches, widespread)

Inflammatory vs. non-inflammatory: Inflammatory alopecia is the result of a disease which targets the hair follicle or shaft. This type of alopecia is the most common form in dogs. Non-inflammatory alopecia is caused by endocrine disorders, and immune-mediated causes which alter normal hair growth.

Alopecia can also vary in terms of localization (a single area or generalized), distribution (symmetric hair loss or asymmetrical), pruritus (itchy or not itchy) and the age of onset.

Possible Causes

There are many conditions and behaviors associated with hair loss. Hair loss generally ties back to one of two root causes: either hair has been removed, ripped out, or licked short; or hair has failed to grow in a particular location. Some of the most common conditions associated with hair loss include:

Allergic responses such as

Flea allergy dermatitisInhalant allergies (atopy)Food allergiesContact allergies

Infections such as

• Dermatophytosis (fungal skin infection) • Bacterial folliculitis • Mites, including Demodex

Disorders affecting normal hair growth such as

HypothyroidismHyperadrenocorticism • Seasonal flank alopecia • Nutritional deficiencies • Alopecia X

• Excessive sex hormone production

Immune-mediated disorders such as

• Pemphigus foliaceous • Alopecia areata

Traumatic Injury such as

• Burns • Scars • FrostbiteSolar damage

Cancer such as

Lymphoma • Chemotherapy/radiation response

Risk Factors

Hair loss is common in dogs. Depending on the cause, the severity can vary widely. In general, it is best to seek vet care as soon as symptoms appear to maximize the effectiveness of treatment and minimize the damage to the skin and hair.

Testing and Diagnosis

The first step in diagnosis is taking a medical history and performing a physical examination looking for signs of fleas, mites, or other obvious causes of itching which can lead to hair loss.  Additional diagnostics for hair loss include:

• Skin scrape • Skin cytology • Trichogram • Fungal/bacterial culture • Wood’s lamp evaluation

• Skin biopsy • Blood work • Therapeutic trials to rule out specific causes

Treatment will depend on the root cause of the hair loss but often includes:

• Medications such as antibiotics/antifungals • Lifestyle changes to remove triggers

• Bathing with specialty treatments • Topical medications • Immunotherapy

Similar symptoms

Alopecia may be confused with normal shedding. If there are no bald patches or rashes, hair loss is normal regardless of volume. Shedding can often be very heavy but it is not a cause for concern.

Associated Symptoms

Itching/skin irritation (pruritus) • Rashes on the skin around the hair loss

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