There are mainly 3 reasons for excess pigmentation (darker colour) on the skin:
Post Trauma pigmentation (called Post Inflammatory pigmentation caused mainly by acne)
Hormonal changes (caused by pregnancy, oral contraceptives)
If the cause of the pigmentation can be eliminated, this is the first action to take. For example, get the acne under control so that no new dark marks are formed. If it is hormonal, such as contraceptives, try to change to another type of contraceptive. This is not so easily done but worth investigating.
What can be done?
The most important step to achieve results is to introduce tyrosinase inhibitors into your skin care routine. These inhibitors will slow down the melanogenesis process in the skin, it is the trigger for the process of melanin production.
Ingredients that are inhibitors are - arbutin, kojic acid, Ascorbic Acid (vit C), mulberry extract, licorice extract to name but a few. Many peptides are also specifically designed to inhibit the melanin process.
Sun protection is also critical when trying to stop excess pigmentation, independent of skin colour. Always apply sun protection every day, re-appy when you will be in the sun for extended periods.
Retinoic Acid can be introduced to the night routine to push the excess melanin out, since it increases cell turnover. It may initially look darker when using this ingredient since it is pushing mlenanin out.
Quick impact can be achieved with TCA treatments such as Mesoestetics Melanoplus. However, this peel does cause significant flaking for 5-7 days. Another treatment option is the Lamelle Retistore Peel or Retistore Plus Peel. It contains Retinoic acid in the second layer that is left on the skin for a minimum of 6 hours. These are all methods to push out excess melanin quickly.
Longer term treatment options are microneedling / Dermapen treatments since it is possible to introduce the inhibitors into the deeper layers of the skin using the channels created by the microneedling device. Here the serums must be customised for tyrosinase inhibition. This has less immediate downtime but will require more treatments. It is also the appropriate steps to take after the more intense TCA treatments to lift the remainder of excess melanin out.
The most important thing to remember in treating this condition is that melanogenesis is an over-active process that can take between 12-18 months to stabilise. You will need to continue tyrosinase inhibition for this period of time to achieve long-term results. It will come back very quickly if the tyrosinase inhibitors are not applied daily or sun protection is not sufficient.