Tanning tends to fade away with weeks to couple of months time.. but due to repeated tanning it can become pigmentation that can set in for longer time..
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Next Steps
Follow the minimal advise .
If still not working out meet a dermatologist so we can discuss problem and have a look at the same time..
For a better solution ..
Take care
Health Tips
Avoid sun exposure to pigmented area for longer time..
Consider antioxidants in diet..
Moisturise skin well..
Scrub gently once in a while 15 days or a month