Use a gentle cleanser and avoid harsh scrubbing
Exfoliate the underarms 1–2 times per week with a mild chemical exfoliant
Apply a fragrance-free moisturizer daily
Switch to a gentle, alcohol-free deodorant
Avoid shaving too closely; use a sharp razor and shaving gel
Consider waxing or laser hair removal if shaving causes irritation
Wear loose, breathable clothing to reduce friction
Use products with niacinamide, azelaic acid, or vitamin C
Try a mild lactic acid or glycolic acid product at night
Apply sunscreen if the underarms are exposed to sunlight
Stop using products that cause irritation or rash
Maintain a healthy weight if friction is contributing
See a dermatologist if the dark marks are sudden, thick, itchy, painful, or spreading