Understand that post-inflammatory hyperpigmentation is the result of the inflammation of the skin. It is most commonly a result of the healing process in the skin. As skin tissue heals, cells secrete chemicals called cytokines that help cause new skin to form in the healing area. However, these cytokines can also stimulate cells called melanocytes. When melanocytes become stimulated, they create more melanin, which is the main pigment in the skin. This causes the skin to become darker. Hyperpigmentation can also be caused by iron being deposited in the skin when red blood cells are broken down after inflammation. One common cause of post-inflammatory skin hyperpigmentation is acne, but any sort of skin injury (such as scrapes, cuts or burns) can cause this condition, as well as other skin conditions (such as eczema).
Know that post-inflammatory skin hyperpigmentation typically goes away on its own over time, though it can linger on some parts of the body (in particular, the legs) for years. Sunlight can cause affected areas to get darker, however, so you should try to limit sun exposure of hyperpigmented areas of the skin, either by covering them with clothing or by using sunscreen (SPF 15 or better) whenever possible. There are some skin-lightening creams that are available over-the-counter (with 0.5 to 2 percent hydroquinone) but there are questions about their effectiveness. Stronger formulations are available from other countries, but these medications can actually worsen the hyperpigmentation not lessen it. As a result, the FDA (according to Skinsight.com) is considering pulling these "bleaching" products from the market.
Realize that if post-inflammatory hyperpigmentation is not going away on its own or if it is causing you distress, a dermatologist may be able to help. This condition can be treated with chemical peels that use one or more of the following compounds: hydroquinone (2-4 percent concentration), tretinoin, glycolic acid, azelaic acid or tazarotene. Microdermabrasion (which uses a rapidly spinning brush to wear away the outer layers of skin) can also be affected. These treatments should only be given by experts, however, because if done incorrectly, chemical peels and microdermabrasion can make the hyperpigmentation worse.