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Seasonal affective disorder can be culprit for canine hair loss

Coming off of a long, dark winter as we are in the Midwest, we're confronted with a unique disease seen in certain breeds of dogs. Light responsive alopecia or seasonal flank alopecia is most often seen at this time of the year. It is not well understood but is thought to be from lack of sunlight
exposure to the pineal gland. The pineal gland is located at the base of the brain and is the gland responsible for telling bears to hibernate and perhaps telling us to crawl into bed early during these long winters, eat fatty foods, and in general, not have much energy.

These changes are not recognized in dogs but physical changes such as trun-cal alopecia and hyperpig-mentation are evident Light responsive alopecia is logically more common in those areas of the country with dark winters such as the Midwest, the Plains states, parts of New England and Canada. Studies of seasonal affective disorder in humans show an incidence of 2 percent in Florida vs. 10 percent in New Hampshire. When seen in other parts of the country or at other times of the year it maybe evident that affected dogs are house bound during the daylight hours for a prolonged period of time. For example, the owner leaves before dawn and arrives home after sunset so the dog is exposed to virtually no natural sunlight. It is not known whether the disease is comparable between humans and animals but what is certain is that a photo period plays a role in both.

Examples of trunkal alopecia with hyperpigmentation due to seasonal flank alopecia


Clinically, the patient is affected with alopecia in a bilaterally symmetrical pattern usually involving the flanks with progressive involvement over the dorsal lumbar area. The hair loss is nonpruritic and maybe accompanied by hyperpigmentation and fol-licular keratosis. The typical clinical picture involves the bilateral flanks but other areas such as the dorsal nasal planum , periocular area, preauricular areas and lateral pinna may be involved. There is no sex predilection and the disease may be hereditary as in our practice we had a mother and daughter Boxer affected. Breeds affected include the Boxer, English Bulldog, French Bulldog, Airedale, Dober-man Pinscher, Bouvier de Flanders, Scottish Terrier, Shar Pei, Labrador Retriever, Giant Schnauzer and Akita. Differential diagnoses include hy-pothyroidism, Cushing's disease and alopecia X.
The diagnosis is made by noting the breed affected, areas of the body affected, time of the year the patient is affected, and by performing skin biopsies. Skin biopsies may include follic-ular atrophy, "foot-like" comedones with excess keratin plugging of the fol-licular infundibula, normal epidermal thickness, and hyperpigmentation of the basal cell layer.


Treatment includes more sunlight exposure and/or melatonin beginning Sept. 23 through March 23 (vernal equinox). The prognosis is good with most patients regrowing hair upon more sun exposure, however some patients skip a year before they regrow hair and some may not regrow hair completely or at all. This appears to be a benign disease but the more common diseases resulting in bilaterally symmetrical alopecia such as Cushing's disease and hypothyroidism should be ruled out.
It is uncertain how the lack of sunlight to the pineal gland results in alopecia of certain specific areas of the body. The role of melatonin release by this gland upon lack of sunlight exposure via the eyes results in depression and lethargy in humans. Prolactin may also play a role as its concentration in the body may be affected by photo period changes and Serotonin concentrations in humans are reduced in dark, cold environments. Oral doses of Melatonin at a range of 3-24mg/day may be helpful in light responsive alopecia. In Canada melatonin injections have been administered on mink farms to cause production of thick coats nonseasonally for the fur industry. It is possible that melatonin injections are more effective than oral melatonin tablets however melatonin injections can be painful. Melatonin has many actions ranging from contraception to use as an antianxiety agent. Its action in seasonal flank alopecia still remains controversial.

A Bulldog With Focal Alopecia November 1999 Veterinary Medicine

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Valene, a 4-year-old intact female English bulldog, presented with a nine-month history of nonpruritic bilateral alopecia and hyperpigmentation of her flanks. The owners reported that the same pattern of hair loss had occurred in the early summer of the two previous years, but oral antibiotic therapy had seemed to resolve the problem. Antibiotic therapy for this year's recurrence resulted in no improvement

The physical examination revealed a patchy, irregular symmetrical alopecia and hyperpigmentation on both flanks. The skin was normotonic, and the hair around the areas did not epilate easily.

Differential diagnoses

Focal alopecia in dogs can be due to folliculitis (e.g. caused by superficial pyoderma, dermatophytosis, demodicosis), endocrinopathy (e.g. hypothyroidism, hyperadrenocorticism, sex hormone imbalance), alopecia areata, and canine recurrent flank alopecia.

Diagnostic tests

Microscopic examination of skin scrapings for mites and a dermatophyte culture were negative. The results of a complete blood count and serum chemistry profile including resting thyroxine concentration were normal. Histopathologic examination of the affected skin revealed a normal epidermis and dermis except for epidermal hypermelanosis. `The hair follicles were filled with keratin, had narrowed follicular ostia and pigmentary incontinence, and were abnormally truncated at their bases with fingerlike projections into the surrounding tissue. The histologic findings confirmed a diagnosis of canine recurrent flank alopecia.


Canine recurrent flank alopecia (also known as cyclic flank alopecia, seasonal flank alopecia, and cyclic follicular dysplasia) is an idiopathic disorder most commonly seen in boxers, bulldogs, Airedales, and schnauzers, although it can affect any breed. Mean age of onset is 4 years (range 8 months to 11 years).1-5 It can affect intact or neutered males and females. Clinical signs include a nonpruritic, noninflammatory, well-demarcated alopecia of the flanks, which is usually bilaterally symmetrical. Sometimes it affects only one flank. Occasionally, alopecia may also involve the dorsum of the nose, base of the tail or ears, and perineum.

In the Northern hemisphere, the onset of alopecia usually is between November and March.2,3 Most dogs regrow their hair within three to eight months, although new hair may have altered pigmentation or regrowth may be incomplete.l-3 In some cases, the hair never regrows. Some dogs losethe same amount of hair each year others lose more and more hair and for longer periods. Also, some affected dogs have only one or two episodes of hair loss.

The cause of this disorder is unknown.