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Seasonal Flank Alopecia in Dogs: Vet’s 2025 Guide 🐶🌤️
By Dr Duncan Houston, BVSc – Ask A Vet Blog
🐾 What is Seasonal Flank Alopecia?
Seasonal flank alopecia—also called cyclic flank alopecia, canine flank alopecia, or recurrent flank alopecia—is a cosmetic skin condition where dogs lose hair in their flank region (the sides just ahead of the rear legs) on a seasonal basis 🍂🌷.
The hair loss typically appears symmetrical on both sides, with the skin in the affected area turning dark and smooth. While the condition is not harmful, it can be distressing for pet owners unfamiliar with its recurring nature or striking appearance 🐕.
📋 Common Characteristics
- 🔘 Symmetrical bald spots on flanks (and sometimes the bridge of the nose)
- 🖤 Darkened (hyperpigmented) skin in bald areas
- 🔁 Often occurs in fall or spring—but may vary by dog
- 💤 Rarely itchy or painful
- 🎨 Hair may regrow a different color—or not at all
- 📅 20% of affected dogs experience only one episode ever
🐶 Breeds at Higher Risk
Though any breed can develop seasonal flank alopecia, it’s more commonly seen in:
- Boxers 🥊
- Airedale Terriers 🧔
- English Bulldogs 🐾
- Bulldog mixes and other short-haired breeds
🔬 What Causes It?
The exact cause is unknown, but it appears to be influenced by the light-dark cycle (photoperiod), which affects melatonin production from the pineal gland 🧠.
Shorter daylight hours in fall/winter are suspected to decrease melatonin, disrupting the hair growth cycle in genetically predisposed dogs.
🧪 How is it Diagnosed?
Diagnosis is usually based on history and appearance of the bald, darkened patches. However, testing may be needed to rule out other conditions such as:
- Hypothyroidism
- Cushing’s disease
- Demodectic mange
- Bacterial or fungal skin infections
🧬 A skin biopsy can confirm the diagnosis if needed, showing characteristic changes in hair follicles and pigmentation.
💊 Treatment Options for 2025
Seasonal flank alopecia doesn’t require treatment unless cosmetic appearance is a concern. But for dogs with predictable or persistent patterns, melatonin therapy can stimulate regrowth 🌱.
1. Oral Melatonin Supplements
- Available over-the-counter (OTC) as capsules or chewables
- Given 2–3 times per day for 4–6 weeks
- Side effects are rare—mostly drowsiness 💤
⚠️ Tip: Choose reputable brands. A 2025 study from the University of Tennessee shows inconsistent melatonin content in low-quality products.
2. Melatonin Implants
A small, rice-sized implant is inserted under the skin (typically between the shoulder blades) and slowly releases melatonin for 4–6 months 💉. This method may be more effective than oral supplements and offers:
- 📅 Long-lasting coverage for an entire season
- 🧪 Consistent hormone delivery
- 💤 Mild drowsiness for 1–3 days post-implantation
Note: Rare cases of sterile abscess at the implant site have been reported, but these are easily managed.
3. Let Nature Take Its Course
Since this condition is not harmful, it’s completely reasonable to do nothing. Hair often regrows on its own as seasons change, especially by late spring or early summer ☀️.
💬 Dr Duncan Houston’s Management Advice
“Seasonal flank alopecia might look alarming, but it's usually just cosmetic. Melatonin is a safe, affordable option if you’d like to try encouraging hair regrowth.” 🩺
🧼 Supportive Skin Care
While melatonin is the primary treatment, supporting your dog’s skin health is also important:
- 🐟 Feed omega-3 fatty acids to nourish skin & coat
- 🧴 Use gentle moisturizing shampoos
- 🌞 Ensure moderate sun exposure—but avoid overexposure in short-coated dogs
📈 Long-Term Outlook
- 20% of dogs experience only one episode
- Most regrow hair within 3–6 months
- Some never fully regrow hair—this is still considered normal
📲 Get Help from Ask A Vet
Worried about your dog’s sudden bald spots? Download the Ask A Vet app to chat 24/7 with licensed vets. We help track patterns, recommend supplements, and schedule melatonin implant options if desired 📱🐾.
