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Why Dogs Shed: Light Cycles, Indoor Living, and When to Worry
Allen Rippy, Veterinarian, Author
Aug 22, 2025
6 min read
For centuries, dogs have adapted their coats to the rhythms of the natural world. In the wild or on farms, dogs shed seasonally, triggered primarily by light cycles—the natural ebb and flow of daylight hours through the year. Longer days in spring signal a heavy shed, as dogs release their thick winter undercoat. Shorter days in autumn cue them to build that insulating coat again.
But when modern life brought dogs indoors under artificial lighting, those cycles blurred. The steady glow of lamps, TV screens, and LED bulbs tells a dog’s body that every day is the same length. Without strong seasonal signals, many dogs now shed lightly year-round rather than in one or two dramatic seasonal blows. This constant, low-level shedding can surprise pet owners, but it’s a normal response to an environment where day and night are artificially leveled out.
Still, how do you know when shedding is normal and when it’s a red flag? Here’s a simple test:
• If you gently tug your dog’s fur and loose hairs come out, but no bare patch appears, that is considered normal shedding. Even if the amount looks dramatic, as long as the coat remains full without bald spots, it’s healthy.
• If, however, you can lightly pull fur and a bald spot forms, that is abnormal hair loss (alopecia). This can point to hormonal imbalances, allergies, infections, or other medical conditions.
One often-overlooked therapy is melatonin, a natural hormone linked to coat growth and seasonal rhythms. In some cases, veterinarians prescribe melatonin supplements for at least three months to help reset the dog’s natural hair cycle, especially in breeds prone to pattern baldness or disrupted shedding.
The takeaway: Shedding is a natural, light-driven process, but indoor living has changed its rhythm. Monitor your dog’s coat closely, and when in doubt—especially if bald spots appear—contact your veterinarian for guidance.