Unfortunately for those of us who live in northeast Ohio, we all know that in winter we get very little natural sunlight. In fact in the winter of 2016, we only had 5 sunny days! In susceptible humans, this can result in Seasonal Affective Disorder (SAD) resulting in depression, overeating, and lethargy. We see the same disease in dogs but with skin changes predominantly.
Dogs need natural sunlight exposure to the pineal gland (the gland that causes bears to hibernate) via the eyes in order to grow hair and have a normal hair/shed cycle. When not enough sunlight is around, dogs will lose hair, sometimes symmetrically (alike on both sides) and gain dark pigment to the skin. The flanks are the most common area affected with the alopecia increasing to over the saddle area. The skin looks normal except for mild flaking with dark pigment sometimes moving up into the area. These dogs are not itchy. Other areas affected include the ear flaps, top of the nose, and sometimes the shoulders.
Breeds where this is seen most commonly are the Boxer, English Bulldog, Wire Haired Pointer, and mixes. Other breeds can have variations of the disease in that if the hair is clipped in the fall (going into the winter season), hair regrowth will not occur till summer or later. Most dogs will regrow hair once the winter is over and they get sun exposure but some dogs will skip a year before hair regrowth. The same problem occurs if steroids are given as they delay hair regrowth.
Other diseases that can mimic this include hypothyroidism, Cushing’s disease (but has lots of other symptoms as well), or steroid use.
Dogs affected with SFA will be “sun seekers” meaning that if sun does occur in the winter, they search it out and want to lie where the sun is coming in through the window (UV light via a window blocks any improvement however). Even though an owner may walk a dog daily in the winter no matter what the weather conditions, it may not be enough sun for that particular dog to grow hair.
Melatonin has been used for SFA but in my opinion, I have not seen it be helpful. The best Rx is getting more sun exposure—at least 15 minutes of natural sunlight daily if possible.
We would be happy to answer any questions on SFA that you may have or write you an Rx for a trip to Florida for the winter!