September Dog Skin Care: Fall Allergy Transition and Coat Change Preparation

Based on peer reviewed veterinary research · For educational purposes only · Updated October 2026 · 8 min read

What Is the Fall Allergy Transition in Dogs?

The fall allergy transition is the shift in September from summer weed and grass pollen to late season pollen, mold spores and early indoor allergens, which can keep atopic dogs itchy or trigger new flares. Atopic dermatitis (an inherited tendency toward allergic skin disease) is estimated to affect 10 to 15% of dogs (Hillier & Griffin, 2001), and these dogs often have a different pattern each season.

In many regions, ragweed continues to release pollen until the first hard frost, so the allergy load of August does not end on September 1. At the same time, falling leaves and damp ground raise mold exposure, and cooler weather sends people and pets indoors, where dust mites and storage mites are present all year. Veterinary guidelines emphasize that many dogs are sensitized to several allergens at once, which is why symptoms rarely switch off cleanly (Olivry et al., 2015).

If your dog itched in August, read our guide to August dog skin care, because the late summer triggers carry forward. Dogs whose itching never fully stops may have year-round triggers, a distinction covered in seasonal vs year-round dog allergies.

Why Do Dogs Shed More in Fall?

Dogs shed more in fall because shorter daylight triggers hair follicles to release the summer coat and grow a denser winter undercoat. Photoperiod, meaning the amount of daylight, is the main signal that controls the hair growth cycle in most dogs, with temperature playing a smaller role. Double coated breeds such as Huskies, Retrievers and Shepherds show the most dramatic change, usually over several weeks.

Normal shedding thins the coat evenly and leaves healthy skin underneath. The concern is when shedding is accompanied by itch, redness, odor or bald patches. Hair loss from skin disease, including allergy, infection and endocrine disorders, can be mistaken for seasonal shedding by owners, which delays treatment. Our article on excessive shedding in large breed dogs explains what separates normal from abnormal shedding.

Regular brushing during the coat change removes loose undercoat, improves airflow to the skin, and lets you see the skin condition. Packed, damp undercoat can hold moisture against the skin, which favors bacterial and yeast overgrowth.

How Do You Tell Normal Shedding From a Skin Problem?

Normal shedding is even, itch-free and leaves healthy skin, while a skin problem usually shows redness, scaling, odor, patchy hair loss or persistent scratching. The distinction matters because secondary infections are common in allergic dogs. International guidelines note that canine superficial bacterial folliculitis is most often secondary to an underlying condition such as allergy, so the infection tends to return unless the cause is addressed (Hillier et al., 2014).

Use the comparison below while brushing your dog.

What Skin Problems Are Common in September?

The most common September skin problems in dogs are allergic flares, Staphylococcus bacterial infections, Malassezia yeast overgrowth and hot spots, all of which are favored by lingering warmth, humidity and itch. Early fall weather is often still warm and wet, which means moisture problems from summer persist while allergens change.

Malassezia dermatitis, a yeast overgrowth, is a frequent complication of allergic skin. WAVD consensus guidelines describe signs of greasy skin, a musty odor, redness and, in chronic cases, dark thickened skin (Bond et al., 2020). It tends to affect the paws, armpits, groin, ears and skin folds.

Hot spots (acute moist dermatitis) develop when a dog licks or scratches a patch of damp, irritated skin until it becomes a rapidly spreading, weeping lesion. Our seasonal guide on preventing hot spots in dogs and our page on hot spots in dogs cover early warning signs. Hot spots are painful, so a dog with a large or deep lesion should be examined.

Treatment and Support Options for Fall Skin Flares

Treatment depends on the underlying cause, and superficial infections confirmed by a veterinarian are often managed with topical antiseptic therapy, with oral medication added for deep or widespread disease. Guidelines favor topical therapy when disease is localized or superficial because it reduces the need for systemic antibiotics (Hillier et al., 2014).

Chlorhexidine is a well studied topical antiseptic with activity against Staphylococcus, and ketoconazole is an azole antifungal that targets Malassezia. Chlorhexidine Spray combines chlorhexidine gluconatewith ketoconazole, so it addresses both organisms commonly involved in fall flares. It is an FDA-registered OTC veterinary drug listed on DailyMed, not a cosmetic, and a spray is convenient for the paws, folds and underbelly.

Topical products support a diagnosis, they do not replace it. If skin has not improved in a few days, lesions are spreading, or your dog is uncomfortable, see your veterinarian. Underlying allergy needs its own long-term plan, outlined in our guide to pollen allergies in dogs.

Prevention and a September Skin Care Routine

A September routine of brushing, pollen removal and weekly skin checks reduces the allergen load and helps you catch problems early. Planning ahead is more effective than reacting once the skin is inflamed.

Brush double coated dogs several times a week during the coat change, and check the skin as you go. Wipe the paws, belly and face after walks to remove pollen and mold spores, and avoid leaving dogs to lie in piles of damp leaves. Wash bedding weekly in hot water and dry it completely. Keep flea prevention current, since fall is still active flea season in many regions.

Once a week, part the coat and examine the armpits, groin, between the toes, inside the ears and around the lips. Redness, odor or small crusts are easier to manage when caught early. For dogs with a predictable allergy pattern, our pre-allergy season checklist can be adapted for the transition into fall.

Frequently Asked Questions

Why is my dog itchy in September?

Ragweed pollen often continues until the first frost, mold increases with fallen leaves, and indoor allergens like dust mites rise as pets spend more time inside. Atopic dermatitis affects an estimated 10 to 15% of dogs, so many have a fall flare.

When do dogs start shedding their summer coat?

Most dogs begin the heavier fall coat change in September as daylight shortens, and it usually lasts several weeks. Double coated breeds show the largest change.

How do I know if hair loss is shedding or a skin problem?

Normal shedding thins the coat evenly and leaves healthy skin. Bald patches, redness, scaling, odor or constant scratching suggest a skin problem and warrant a veterinary exam.

Can I bathe my dog during the fall coat change?

Yes, bathing and thorough drying can help remove loose undercoat and pollen. Dry fully to the skin, since damp undercoat can encourage bacterial and yeast overgrowth.

Sources

1. Hillier A, Griffin CE. The ACVD task force on canine atopic dermatitis (I): incidence and prevalence. Veterinary Immunology and Immunopathology. 2001;81(3-4):147-151.
2. Olivry T, DeBoer DJ, Favrot C, et al. Treatment of canine atopic dermatitis: 2015 updated guidelines from the International Committee on Allergic Diseases of Animals (ICADA). BMC Veterinary Research. 2015;11:210.
3. Hillier A, Lloyd DH, Weese JS, et al. Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases). Veterinary Dermatology. 2014;25(3):163-e43.
4. Bond R, Morris DO, Guillot J, et al. Biology, diagnosis and treatment of Malassezia dermatitis in dogs and cats: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology. Veterinary Dermatology. 2020;31(1):27-e4.

Related Reading

• August Dog Skin Care: Late Summer Infections, Ragweed, and Post-Swim Routines
• Excessive Shedding in Large Breed Dogs: Causes and What Helps
• Seasonal vs Year-Round Dog Allergies Explained

E. Maddens

Founder of Vetified. Develops topical antifungal and antimicrobial formulations for companion animals. Vetified products are listed on DailyMed and manufactured through FDA-registered facilities in the United States.

Research basis: All Vetified content references peer reviewed research published in journals including Veterinary Dermatology, JAVMA, and Journal of Small Animal Practice.