ELI5: Why a Mole Keeps Crusting?

A mole keeps crusting because the skin there is damaged or irritated and is trying to heal itself by making a scab, but the spot keeps getting re-injured or the cells underneath are not healthy.

Think of a mole like a little brown hill on your skin. Just like the rest of your body, it has a smooth blanket of skin over it to protect it. When that blanket gets torn, your body quickly sends a bandage made of dried blood and skin cells, which we call a crust or a scab.

Normally, a scab falls off once the skin underneath is all better. But sometimes, a mole gets stuck in a loop of making a crust over and over. Here is why that happens in everyday life:

• Rubbing and scratching: Moles stick out a little bit. If a shirt collar, bra strap, or waistband keeps rubbing against it every day, it scrapes the scab off before it can finish healing.
• Accidental bumping: If you accidentally scratch it with your fingernails or nick it while shaving, the skin breaks open again, and your body has to build a brand new crust.
• Confused skin cells: Sometimes, the tiny building blocks of the skin, called cells, get confused or sick. When cells misbehave, like in a skin problem called melanoma or skin cancer, they make the skin fragile and weak. The mole keeps bleeding, oozing, and crusting all on its own, even if nothing touches it.