Alopecia in Dogs: Causes, Diagnosis, and Treatment

What is alopecia in dogs?

Alopecia refers to the complete or partial loss of hair in localized or widespread areas of the body—without regrowth. As a symptom, rather than a diagnosis in its own right, alopecia is one of the most common reasons for visits to veterinary dermatology clinics. Causes range from parasites and fungal infections to hormonal imbalances and genetically determined hair follicle defects.

The most clinically important distinction: Is the alopecia pruritic (associated with itching) or non-pruritic? This distinction alone greatly narrows down the range of possible causes and determines the direction of the diagnosis.

Background + Scientific Context

Welle (2023, Veterinary Pathology, PubMed 37191329) systematically classifies canine non-inflammatory alopecia: Congenital forms result from abnormalities in hair follicle development (e.g., genetically based ectodermal dysplasias). Postnatally acquired forms include follicular dysplasias with a breed predisposition, as well as alopecia caused by endocrinopathies, circulatory disorders, or stress.

Müntener et al. (2012, Veterinary Dermatology, PubMed 22575019) demonstrated histologically that all alopecia groups—Alopecia X, hypothyroidism, hyperadrenocorticism, and seasonal alopecia—exhibit a significantly increased proportion of inactive telogen follicles: a hallmark of impaired anagen induction. Alopecia X exhibited the lowest anagen and highest telogen ratios of all groups.

Frank et al. (2003, Veterinary Dermatology, PubMed 12662266) examined 276 dogs with non-pruritic alopecia after ruling out hypothyroidism and hyperadrenocorticism: Elevated levels of sex hormone intermediates were found in 73% of the dogs. Breed-specific patterns were pronounced—Spitz-type dogs and Siberian Huskies showed elevated progesterone levels; this underscores the need for breed-specific reference values.

Vitomalia-Position

Alopecia is always a symptom with an underlying cause—it is not a natural characteristic of the coat or a cosmetic issue. We view the trivialization of hair loss as problematic: Bald patches can be a sign of treatable conditions such as hypothyroidism, parasitic infestations, or fungal infections. Any new, persistent, or spreading alopecia should be evaluated by a veterinarian—not months later.

When does alopecia in dogs become a concern?

• For well-defined bald patches that spread within weeks
• In cases of symmetrical alopecia (e.g., on both sides of the flanks or trunk) — indicative of an endocrine cause
• If itching, scratching, and licking occur simultaneously — this may indicate atopy, parasites, or dermatophytes
• For puppies and young dogs suspected of having breed-related dysplasia
• As a concomitant symptom of changes in blood counts detected during routine examinations
• After ruling out normal seasonal shedding (hair loss ≠ alopecia)

Practical application

Pruritic vs. non-pruritic — setting the initial course:

Common causes:

• Hypothyroidism: Symmetrical, bilateral alopecia, often accompanied by weight gain and lethargy. Diagnosis: Total T4 + TSH stimulation test.
• Hyperadrenocorticism (Cushing's syndrome): abdominal alopecia, thin skin, polydipsia/polyuria. Diagnosis: ACTH stimulation test.
• Alopecia X / Sex Hormone Alopecia: Common in Nordic breeds (Spitz, Samoyed, Chow Chow). Symmetrical alopecia without systemic signs — diagnosis by exclusion.
• Follicular dysplasia / color-dilution alopecia: Genetic, common in dogs with dilution genes (blue, isabella). Histologically detectable by the presence of melanin clumps in the follicles.
• Demodex: Scaly lesions around the eyes and on the paws; not itchy in the early stages. Diagnosis by skin scraping.

Diagnostic procedure:

1. Medical history: onset, course, itching, systemic signs, breed-related risk
2. Skin scrapings (Demodex, Sarcoptes) and, if necessary, fungal culture
3. Complete blood count + thyroid function tests (T4, TSH)
4. ACTH stimulation test / Low-dose dexamethasone test for suspected Cushing's syndrome
5. Biopsy: Hendricks et al. (2021, PubMed 33047299) recommend a combination of transverse and vertical incisions for a complete follicular diagnosis

Common Mistakes & Myths

• "Hair loss in the spring is always part of the normal seasonal shedding cycle." Seasonal shedding is bilateral, diffuse hair loss followed by regrowth. Alopecia is persistent hair loss without regrowth—bald patches after the seasonal shedding cycle are not normal.
• "Biotin supplements help the coat grow back." Taking supplements without a diagnosis does not address the underlying cause. Biotin is ineffective in cases of hormonal or parasitic alopecia.
• “It’s not just older dogs that have hormonal problems.” Follicular dysplasia and alopecia X often begin in young adulthood—so age alone does not rule out hormonal disorders.

Current State of Research (2026)

The histopathological classification of canine alopecia has been refined by Welle (2023) and Müntener et al. (2012). Genetic markers for breed-specific dysplasias are the subject of current research. Simple blood biomarkers for Alopecia X are still lacking—the diagnosis remains a diagnosis of exclusion. A combination of clinical, hormonal, and histological diagnostics is the gold standard.

Frequently Asked Questions

What are the most common causes of alopecia in dogs?

Hormonal disorders (hypothyroidism, Cushing’s syndrome, alopecia X), parasitic infestations (Demodex, Sarcoptes), fungal infections (dermatophytes), and genetic follicular dysplasias. Distinguishing between pruritic and non-pruritic conditions is the first step in clinical differentiation.

Can alopecia in dogs go away on its own?

Seasonal alopecia (recurrent flank alopecia) may resolve spontaneously. Alopecia caused by untreated hypothyroidism, parasitic infestation, or follicular dysplasia will not improve without treatment. Any persistent or progressive alopecia requires veterinary evaluation.

How is alopecia diagnosed in dogs?

Step-by-step: Medical history, skin scraping, fungal culture, complete blood count, and hormone levels (T4, cortisol); if necessary, a biopsy using a combined incision technique (transverse + vertical). The specific diagnosis determines the treatment plan—there is no one-size-fits-all treatment for alopecia.

Related terms

• Hypothyroidism in Dogs
• Atopic Dermatitis in Dogs
• Demodex in Dogs
• Complete Blood Count for Dogs
• Symptom: Dog
• Dog Grooming

Sources & Further Reading

1. Welle, M. M. (2023). Canine noninflammatory alopecia: An approach to its classification and a diagnostic aid. Veterinary Pathology, 60(6), 748–769. https://pubmed.ncbi.nlm.nih.gov/37191329/

2. Müntener, T., Schuepbach-Regula, G., Frank, L., Rüfenacht, S., & Welle, M. M. (2012). Canine noninflammatory alopecia: a comprehensive evaluation of common and distinguishing histological characteristics. Veterinary Dermatology, 23(3), 206–e44. https://pubmed.ncbi.nlm.nih.gov/22575019/

3. Frank, L. A., Hnilica, K. A., Rohrbach, B. W., & Oliver, J. W. (2003). Retrospective evaluation of sex hormones and steroid hormone intermediates in dogs with alopecia. Veterinary Dermatology, 14(2), 91–97. https://pubmed.ncbi.nlm.nih.gov/12662266/

4. Hendricks, A., Stevens, K., Brooks-Brownlie, H., Patterson-Kane, J., & Bond, R. (2021). Transverse sectioning in the evaluation of skin biopsy specimens from alopecic dogs. Journal of Small Animal Practice, 62(4), 261–270. https://pubmed.ncbi.nlm.nih.gov/33047299/