Why does my dog have matted fur on its legs and armpits?

Read time: 3 minutes

Overview

Matted fur on a dog’s legs and armpits is often caused by friction, moisture, dirt or a coat that isn’t being brushed all the way through. These areas rub easily when your dog walks, lies down or plays, so tangles can form quickly and tighten over time.

It’s usually a grooming issue, but skin irritation, discomfort or an underlying coat problem can sometimes play a part. The good news is that there are a few simple things you can check at home before deciding what to do next.

Things To Check

1. Check whether the mats are soft and loose or tight and close to the skin.

2. Look for redness, heat, broken skin, scabs, discharge or any bad smell around the area.

3. Notice whether the fur is getting matted after wet walks, swims, rain, or time in long grass.

4. See if your dog seems sore, restless or sensitive when you touch those areas.

5. Check whether the coat is shedding heavily, especially if loose undercoat is getting trapped.

6. Think about whether the armpits or legs are rubbing against a harness, collar, bedding or clothing.

7. Look for signs of licking, chewing or scratching that could be making the coat worse.

Common Causes

The most common cause is simple coat friction. The legs and armpits move a lot, so hair there can knot more easily than in other areas.

Moisture can make matters worse. Damp fur from rain, washing or muddy walks can clump together, especially in longer or thicker coats.

Loose undercoat is another common reason. If a dog is shedding and the dead coat isn’t brushed out, it can compact into tangles and mats.

Sometimes mats start because something is irritating the skin. Licking, scratching or rubbing may lead to knots, and the fur can also mat more easily if the skin is sore.

Less commonly, poor coat condition, reduced mobility or a grooming routine that’s not quite matching the coat type can contribute to repeated matting.

What To Do

Start by gently checking how tight the mats are. Small, loose tangles are often easier to manage than larger mats that have pulled close to the skin.

If the coat is only lightly tangled, regular brushing with the right tool for your dog’s coat type may help prevent the area from tightening up again. Work slowly and avoid pulling, especially in the armpits where the skin is delicate.

After wet walks or bathing, dry the coat thoroughly, especially in the folds behind and under the legs. Keeping these areas clean and dry can make a real difference.

If a harness seems to be rubbing, check the fit and look for signs that it’s causing repeated friction in the same place. You may also find it helps to keep the coat trimmed neatly in high-friction areas if that suits your dog’s coat and grooming routine.

If the mats are tight, sore or close to the skin, it’s usually better not to try to force them out. A professional groomer or your vet may be able to advise on the safest way to deal with them.

Products That May Help

For dogs with coat tangles, regular washing and grooming can help support day-to-day coat care, especially if the fur is picking up dirt, moisture or debris in high-friction areas like the legs and armpits.

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