Home » Diseases » In dogs » CRFA Flank Alopecia (Cyclical Recurrent Hair Loss on the Flanks)

CRFA Flank Alopecia (Cyclical Recurrent Hair Loss on the Flanks) in Dogs

Occurrence: rarer
Location of illness: Abdomen/pelvis, Skin/Fur

Author: Dr. med. vet. Gisa Löwe | Last modified: 06.11.2025

Cyclical RecurrentRecurrent refers to a disease that repeatedly returns or worsens after a temporary remission or improvement. Flank Alopecia (CRFA) is a dermatological condition in dogs characterized by seasonal or periodic hair loss, mostly on the flanks. This condition often occurs in autumn or winter and is caused by a disturbance in the hair growth cycle.

The most important facts at a glance

CanineCanine refers to anything related to dogs. The term is used to describe characteristics, diseases, or specific aspects that specifically affect dogs. RecurrentRecurrent refers to a disease that repeatedly returns or worsens after a temporary remission or improvement. Flank Alopecia (CRFA) is a condition that leads to seasonal hair loss on the flanks in dogs. The hair cycle is disrupted by a prolonged resting phase, which leads to hair loss. The exact cause is still unknown, but hormonal fluctuations, especially of melatonin levels, are suspected to play a role. Melatonin, which is influenced by daylight, can become unbalanced in autumn and winter, triggering the disease. Genetic factors also contribute to susceptibility, with certain breeds such as Boxers and Bulldogs being more commonly affected. Symptoms include seasonal hair loss, thin fur, and occasionally itchy, scaling skin. DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is based on clinical observation and exclusion of other causes. Treatment is often not necessary as the condition is mostly cosmetic and the hair regrows in spring or summer. If desired, melatonin can be administered under veterinary supervision to normalize the hair growth cycle. Increasing the amount of light the dog receives in winter can also be helpful. The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. is good as the condition does not cause health problems. Preventive measures include increasing the amount of daylight in winter and possibly the prophylactic administration of melatonin. Research focuses on genetic and environmental factors as well as the development of new treatment options.

Causes

Hair growth in dogs occurs in cycles consisting of a growth phase (anagen), a transition phase (catagen), and a resting phase (telogen). In CRFA, there is a disturbance of this cycle, especially a prolonged telogen phase, which leads to hair loss.

The exact mechanism that leads to CRFA is not yet fully understood. It is believed that the condition is related to a disturbed melatonin level, a hormoneHormones are chemical messengers produced by endocrine glands and released into the bloodstream to affect specific cells or organs in the body. They regulate numerous bodily functions, including growth, metabolism, and reproduction. that controls the sleep-wake rhythm and seasonal changes in the body. Melatonin is produced by the influence of daylight on the pineal gland, and a reduction in daylight in autumn and winter can lead to an imbalanceImbalance refers to an imbalance or disruption of normal function or composition in the body, which can lead to health problems..

Genetic factors also play a role, as certain breeds such as Boxers, Bulldogs, and Airedale Terriers are more frequently affected. This suggests that a genetic predispositionA predisposition is an innate inclination or susceptibility of an organism to certain diseases or conditions. In dogs and cats, there may be a genetic predisposition to certain conditions such as hip dysplasia or certain heart diseases. plays a role in the susceptibility to CRFA.

Symptoms

Very common symptoms:

Common symptoms:

Cutaneous Hyperpigmentation

The main symptom of CRFA is symmetrical alopecia on the dog’s flanks, that is, on both sides of the body. This hair loss can also include other areas such as the back or sides, but often remains limited to the flanks.

Apart from the hair loss, the skin in the affected regions often shows dark pigmentation (hyperpigmentationHyperpigmentation is a skin condition in which certain areas of the skin become darker than the surrounding skin. This can be caused by an overproduction of melanin, sun exposure, inflammatory conditions, or other factors.). The skin may appear smooth and shiny, but generally shows no signs of inflammation or itching.

The affected dogs usually do not show systemic symptoms such as fever or loss of appetite. The condition is mainly cosmetic and does not affect the general well-being of the dog.

Diagnosis

The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of CRFA is primarily based on the clinical presentation and the exclusion of other causes of hair loss. The veterinarian will take a thorough historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits. to determine if the hair loss is seasonal or cyclical.

Skin biopsies can be performed to rule out other dermatological conditions. These biopsies typically show a prolonged telogen phase of the hair follicles, which is characteristic of CRFA.

Additional diagnostic tests may include blood tests to rule out hormonal imbalances such as hypothyroidism, which can also cause hair loss.

Therapy

Since CRFA is usually a cosmetic condition, treatment can often be avoided unless the dog’s owner wants to improve its appearance. One possible treatment is the administration of melatonin, which can help normalize the hair growth cycle. However, melatonin should only be used under veterinary supervision, as the dosage is important.

In some dogs, improving living conditions, such as increasing the amount of daily light or providing UV light sources in the winter months, can be helpful. This can help regulate the natural melatonin level.

There is no specific drug therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. that can cure CRFA, as the disease is usually self-limitingSelf-limiting conditions are conditions that resolve on their own without medical intervention. In dogs and cats, mild viral infections or gastrointestinal disturbances can often be self-limiting. and the hair usually grows back on its own in the spring or summer.

Prognosis and follow-up care

The prognosis for dogs with CRFA is excellent, as the condition is usually only cosmetic and does not cause any health problems. The hair loss is temporary, and the hair usually grows back once the seasonal conditions change.

However, some dogs may experience recurring episodes of CRFA year after year. In these dogs, long-term monitoring and occasional treatment may be necessary to improve their appearance.

Prevention

The preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. of CRFA is difficult because the exact cause is not fully understood. However, certain measures can help reduce the risk or alleviate the symptoms.

One way is to increase the amount of daylight the dog receives, especially in the winter months. This can be achieved by taking longer walks outdoors during the day or using special UV lamps indoors.

For dogs that are repeatedly affected, a prophylactic administration of melatonin can be considered to support hair growth. However, this should always be done in consultation with a veterinarian to ensure the correct dosage and safety.

Outlook on current research

Cyclical recurrent hair loss on the flanks, also known as CanineCanine refers to anything related to dogs. The term is used to describe characteristics, diseases, or specific aspects that specifically affect dogs. RecurrentRecurrent refers to a disease that repeatedly returns or worsens after a temporary remission or improvement. Flank Alopecia (CRFA), is a common but poorly understood condition in dogs. Current research focuses on identifying the exact causes of this disease. Scientists suspect that hormonal fluctuations related to daylight lengths may play a role. This is supported by the observation that the disease often occurs in the autumn and winter months when the days get shorter.

A significant research approach is to understand the genetic predispositions that lead to this disease more frequently in certain breeds. Breeds such as Boxers, Bulldogs, and Airedale Terriers appear to be more susceptible. Genetic studies aim to identify specific hereditary traits that increase the risk for CRFA. In addition, it is being investigated whether environmental factors, such as diet and lifestyle, have an influence on the occurrence of the disease.

Another important area of research is the development of treatment options. Currently, there is no specific cure for CRFA, and treatment is mostly focused on relieving the symptoms. Researchers are working to develop new drugs and therapies that can stimulate hair growth and reduce hair loss. These include hormonal treatments and nutritional supplements that improve skin health.

Recently, research has also expanded to the role of the microbiome in the context of skin health and hair loss in dogs. Scientists are investigating how a balanced intestinalIntestinal refers to the intestine, the part of the digestive tract that extends from the stomach to the anus. Intestinal diseases affect the small and/or large intestine. flora can strengthen the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. and potentially help reduce the risk of CRFA. Studies that shed light on the interaction between intestinalIntestinal refers to the intestine, the part of the digestive tract that extends from the stomach to the anus. Intestinal diseases affect the small and/or large intestine. bacteriaBacteria are microscopic, single-celled organisms that exist in almost every environment on Earth. Some types of bacteria are beneficial or even essential to life, while others can cause disease. and skin diseases in dogs could open up new approaches to the preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. and treatment of CRFA.

In summary, research on CRFA is still in its early stages, but is progressing steadily. With the increasing knowledge about the genetic, hormonal, and environmental factors that contribute to the development of this disease, scientists hope to develop more effective diagnostic and therapeutic methods in the near future.

Frequently asked questions (FAQs)

What is cyclical recurrentRecurrent refers to a disease that repeatedly returns or worsens after a temporary remission or improvement. hair loss on the flanks in dogs? Cyclical recurrentRecurrent refers to a disease that repeatedly returns or worsens after a temporary remission or improvement. hair loss on the flanks, also called CRFA, is a skin condition in which dogs lose hair on their flanks during certain seasons. The loss is usually symmetrical and affects both sides of the body.
Which dogs are most commonly affected? CRFA often occurs in certain breeds, including Boxers, Bulldogs, Airedale Terriers, and Schnauzers. Other breeds may also be affected, but these breeds seem to have a higher predispositionA predisposition is an innate inclination or susceptibility of an organism to certain diseases or conditions. In dogs and cats, there may be a genetic predisposition to certain conditions such as hip dysplasia or certain heart diseases..
What are the main causes of CRFA? The exact causes are not yet fully understood, but it is believed that hormonal fluctuations related to daylight length play a role. Genetic factors may also play a role.
How is CRFA diagnosed? The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of CRFA is mainly based on the clinical examination and the exclusion of other causes of hair loss. A veterinarian may also perform skin biopsies and blood tests to rule out other conditions.
Is there a cure for CRFA? Currently, there is no specific cure for CRFA. Treatment focuses on relieving the symptoms and promoting hair growth, often with the help of nutritional supplements and hormonal therapies.
Can CRFA be prevented? Since the exact causes of CRFA are not fully understood, specific preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. is difficult. A balanced diet and a healthy lifestyle could potentially reduce the risk.
Are there home remedies that can help? Some dog owners report positive results with the use of coconut oil or special shampoos to support skin health. However, it is important to use such remedies in consultation with a veterinarian.
What role does nutrition play in CRFA? Nutrition can play an important role in skin health. A balanced diet that contains essential fatty acids and vitamins can help strengthen the skin and promote hair growth.
How can I help my dog with CRFA? In addition to veterinary treatment, you can help your dog by paying attention to good skin care, reducing stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being., and providing him with a balanced diet. Regular veterinary check-ups are also important.
When should I take my dog to the vet? If you notice unusual hair loss in your dog, you should see a veterinarian to clarify the cause. Early diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and treatment can help mitigate the course of the disease.