Wash the neck gently twice daily with a mild cleanser
Exfoliate 1 to 2 times per week with a gentle chemical exfoliant like lactic acid or glycolic acid
Moisturize daily with a lotion containing urea, lactic acid, or ceramides
Apply sunscreen to the neck every day
Avoid harsh scrubbing, friction, and tight collars
Maintain a healthy weight if excess weight is contributing to skin folds
Treat any underlying causes such as diabetes, insulin resistance, or hormonal issues
Use topical products with niacinamide, vitamin C, azelaic acid, or retinoids if suitable
Stay consistent for several weeks to months
See a dermatologist if the darkening is sudden, thick, itchy, or not improving