🍂 Vet-Approved Guide to Seasonal Flank Alopecia in Dogs (2025) 🐶

By Dr Duncan Houston BVSc

Seasonal Flank Alopecia (SFA)—also known as cyclic flank alopecia or recurrent flank alopecia—is a harmless but often puzzling condition where dogs lose hair in a seasonal pattern 🧬. In this 2025 guide, Dr Duncan Houston explains what causes it, which breeds are affected, and how melatonin therapy may help 🩺.

🔍 What Is Seasonal Flank Alopecia?

SFA is a non-itchy, non-painful condition where dogs lose patches of hair—usually on both flanks (sides near the hind legs)—once or twice a year 🌤️. Hair loss typically starts in the fall or spring and may reverse as the seasons change. Some dogs never regrow hair, while others regrow it in a different color 🎨.

• 🐾 Common sites: flanks, sometimes bridge of the nose
• 🟤 Affected skin may become dark (hyperpigmented)
• 🔁 Can recur yearly—or skip years altogether
• ✅ Cosmetic only; not harmful to health

🐶 Breeds Most Affected

SFA can affect any breed, but it’s most commonly seen in:

• 🐕 Boxers
• 🐩 Airedale Terriers
• 🦴 English Bulldogs

Dogs of all ages may be affected, but the average age of onset is around 4 years 📆.

📸 What It Looks Like

• 📍 Symmetrical bald patches on both sides
• 🎨 Dark skin pigmentation (not red or inflamed)
• 🩹 Some dogs may have mild skin infection at the site

The condition is typically diagnosed based on its classic appearance and seasonal pattern. A skin biopsy can be performed for confirmation 🧫.

🧠 What Causes It?

The exact cause is unknown, but light exposure and hormonal changes are suspected triggers 🌞🌒. The pineal gland responds to daylight cycles and produces melatonin—when days get shorter, melatonin levels drop, possibly triggering hair cycle disruptions.

Genetics also appear to play a role, given breed predisposition 🧬.

💊 Treatment Options

Good news: SFA is purely cosmetic, and treatment is optional. However, many owners seek solutions for aesthetic or grooming reasons 🛁.

1. 🌿 Oral Melatonin Supplementation

Melatonin is a natural hormone that helps regulate circadian rhythms. It may stimulate hair regrowth when used regularly during shedding seasons 🕰️.

• 💊 Typically given 2–3 times daily
• 🕐 Start 4–6 weeks before usual onset of hair loss
• 😴 May cause mild drowsiness in some dogs

Important: Melatonin is sold as a supplement and not regulated like prescription drugs. Always use a trusted veterinary brand and confirm dosage with your vet ✅.

2. 💉 Melatonin Implants

Newer melatonin implants offer more consistent results:

• 📦 Implanted under the skin between the shoulders
• 🕓 Lasts 4–6 months per implant
• 🧴 Minimal side effects; rarely causes minor swelling or sterile abscess

Implants are ideal for dogs who don’t tolerate pills or for busy households wanting less maintenance 🐾.

🔬 Diagnosis

Most cases are diagnosed visually and with history alone. However, your vet may recommend:

• 🔬 Skin cytology: to rule out infections
• 🧪 Skin biopsy: for confirmation in atypical cases
• 🔍 Rule-out of thyroid disease or other endocrine issues if additional signs are present

📈 Prognosis

• ✅ Excellent—SFA is a cosmetic issue
• 🔁 About 20% of dogs only have one episode
• 📉 Some dogs never regrow the lost hair

Most dogs live full, healthy lives with or without treatment 💪. Hair regrowth may happen over weeks or months, often with seasonal shifts 🗓️.

🧼 When to Treat

You may want to treat if:

• 🎨 Your dog’s appearance is significantly affected
• 🪮 You want to reduce seasonal shedding concerns
• 📸 You're preparing for shows or public events

But if your dog is happy, active, and otherwise healthy, treatment is not medically necessary 🐕❤️.

📲 Final Advice from Dr Duncan Houston

Seasonal flank alopecia may look dramatic—but rest assured, it’s not dangerous. With the support of your vet, you can decide whether to treat it or simply monitor it seasonally 🌿.

💡 Curious about melatonin options, implant availability, or skin care for alopecia-prone pets? Download the Ask A Vet App or visit AskAVet.com for guidance and product tips any time 🐾📱.