Skin infections on dogs typically show up as some combination of redness, hair loss, scabs, bumps, and flaky or greasy skin. The exact appearance depends on what’s causing the infection, whether bacterial, yeast, or fungal, but most infections share a few hallmarks: the skin looks noticeably different from the surrounding area, your dog can’t stop scratching or licking the spot, and the problem tends to spread or worsen over days rather than resolving on its own.
Bacterial Infections: The Most Common Type
Bacterial skin infections (called pyoderma) are by far the most frequent skin infections in dogs, and they come in two levels of severity. Superficial infections sit near the skin’s surface and typically look like bald patches, small bumps or welts around hair follicles, scabs, and excessive flaking. The flaking is often the first thing owners notice. Scales may appear pierced by hairs, almost like tiny collars of dead skin circling individual hair shafts.
In shorthaired breeds like Pit Bulls, Boxers, and Dalmatians, superficial bacterial infections can look a lot like hives. The inflammation around each hair follicle pushes the hair upright, creating a bumpy, raised texture across a patch of skin. In longhaired dogs, you’re more likely to notice a dull coat, unusual shedding, and scaly skin hiding underneath the fur.
Deep bacterial infections are harder to miss. They cause pain, swelling, bloody or pus-filled discharge, and a strong foul odor. You may see firm nodules under the skin, open sores that ooze, or crusted areas with matted, sticky fur on top. In longhaired breeds especially, the fur can become matted over the infected area, trapping moisture and making everything worse.
Yeast Infections: Greasy, Dark, and Smelly
Yeast infections look and feel distinctly different from bacterial ones. The skin often becomes greasy or waxy with a yellowish or slate-gray tone. Over time, the affected area thickens and darkens, taking on a leathery, almost elephant-like texture. This thickening and darkening tends to happen gradually, so owners sometimes don’t realize how much the skin has changed until the infection is well established.
The smell is often the giveaway. Yeast infections produce a strong, musty odor that many owners describe as unpleasant and persistent. The infection tends to strike areas where moisture gets trapped: between the toes, inside ear flaps, around the groin, and in any skin folds. If your dog’s paws smell unusually sour or their ears look waxy and irritated, yeast is a common culprit.
Ringworm: Circular Patches of Hair Loss
Ringworm isn’t caused by a worm at all. It’s a fungal infection, and its signature look is round patches of hair loss with crusty, scaly borders. The patches often have redness at the edges and may contain small bumps or pustules. Multiple circular bald spots can appear at the same time across different parts of the body.
Ringworm is worth knowing about because it’s contagious to humans and other pets. The lesions can look similar to other causes of hair loss in dogs, so a vet visit is important for confirmation. Unlike bacterial infections, ringworm patches aren’t always intensely itchy, which can make them easier to overlook early on.
Hot Spots: Red, Wet, and Fast-Moving
Hot spots are small areas of skin that appear red, moist, irritated, and inflamed, often seemingly overnight. They literally feel warm to the touch. They’re most commonly found on a dog’s head, hips, or chest, and they can expand rapidly as the dog licks and chews at the area.
These spots often start with something else: an ear infection can trigger a hot spot under the ear flap, an anal gland issue can lead to one under the tail, or a tangle of matted fur can trap enough moisture to kick things off. The initial trigger may be hidden, especially in dogs with thick coats or curly tails, so it’s worth checking around the ears, under the tail, and beneath any mats if you spot one.
Where Infections Show Up First
Certain areas of your dog’s body are more infection-prone than others. Skin folds trap warmth and moisture, creating ideal conditions for bacteria and yeast to multiply. The belly, especially the hairless portions in puppies, is a common spot for pus-filled blisters that break open and crust over. Paws and ears are frequent targets for yeast. Areas that stay damp after swimming or bathing, particularly under floppy ears, are especially vulnerable.
Some breeds are predisposed to skin fold infections specifically because of their anatomy. English Bulldogs, French Bulldogs, Pugs, Basset Hounds, Chinese Shar-Peis, Boxers, English Cocker Spaniels, and Cavalier King Charles Spaniels all carry higher risk. In these breeds, infections develop in facial folds, around lip flaps, near corkscrew tails, and anywhere skin doubles over on itself. The severity can range from mild redness to deep, painful ulceration where secretions accumulate and soften the skin.
How to Tell Infection From Allergies
This is one of the trickiest parts for dog owners, because allergies and infections often occur together. A dog with allergies scratches constantly, creating tiny breaks in the skin that bacteria and yeast then exploit. So what starts as an allergic rash can become an infection on top of an allergy.
A few visual cues can help you distinguish them. Pure allergic reactions tend to cause diffuse redness and itching without much discharge, odor, or crusting. Once infection sets in, you’ll typically see one or more of these additions: pus or discharge, a noticeable smell, scabs and crusts, hair loss in distinct patches, or skin that’s thickened and discolored. If your dog has been scratching for a while and the skin now looks worse rather than better, with any of those signs layered on top, infection is likely involved.
What a Vet Will Do to Confirm It
Visual appearance alone is often suggestive but not enough for a definitive diagnosis. Your vet will likely perform a simple, painless skin test right in the exam room. The most common method uses a small strip of adhesive tape pressed against the affected skin, which picks up surface cells and microorganisms for examination under a microscope. This works well for flaky, greasy, or eroded areas and for tricky spots like between the toes.
For oozing or crusted lesions, the vet may press a glass slide directly against the area or swab it with a cotton tip. If the infection is deeper, with nodules or swelling beneath the skin surface, a small needle sample may be taken. These tests help identify whether bacteria, yeast, or fungi are responsible, which matters because each requires different treatment. In cases that don’t respond to initial treatment, a bacterial culture can pinpoint the exact organism involved and which medications will work against it.