Black crusty spots on skin: possible causes and care

A spot after squeezing, shaving or scratching often forms a small scab. A new dark crust without an obvious injury, particularly one that changes, bleeds repeatedly or will not heal, needs an in-person skin examination.

Acne can present with inflamed pimples that crust after they rupture or are picked. Folliculitis produces inflamed spots centred on hairs, while razor bumps follow shaving and may leave dark marks in richly pigmented skin.

Location and texture narrow the possibilities: note whether each lesion began as a bump, blister or wound, whether it itches or hurts, and whether there is pus, warmth, a central hair, an irregular border or continuing growth.

Clean the skin gently with water and a mild cleanser, pat dry and avoid picking. If clothing rubs the spot, cover it with a clean non-stick dressing and change the dressing when damp or dirty.

Pause shaving over inflamed lesions and do not apply bleach, acids or harsh scrubs to remove the dark colour. Take a well-lit photograph with a size reference so that you can track genuine change rather than relying on memory.

Get urgent medical help for rapidly expanding black or purple skin, severe pain, fever, spreading redness, swelling, pus, red streaks, blistering after a burn or chemical exposure, or dark tissue with numbness or coldness.

See a dermatologist for a spot that repeatedly scabs or bleeds, changes in size, shape or colour, develops an uneven edge, or does not heal. These features require direct assessment and cannot be diagnosed reliably from colour alone.

Ask whether the crust should be left intact, whether infection testing or a closer skin examination is needed, which dressing is suitable, what changes to photograph, and when a biopsy would be considered for a persistent lesion.