The development of dark marks after acne treatment can be a significant issue for patients with pigmented skin types. The medical name for this phenomenon is post-inflammatory hyperpigmentation.

Pigment in the skin is produced by a specialized population of cells known as melanocytes. These are situated between the thin surface layer of the skin (the epidermis) and the thicker, deeper layer that give the skin its strength (the dermis). Inflammation occurring in acne can cause melanocytes to produce additional pigment, additionally inflammation causes death of melanocytes and as a consequence they fall deeper within the skin where they are engulfed by immune cells.

Whilst these dark marks will fade with time, they can persist for many months after acne lesion have resolved and for some patients can be a greater concern than the acne lesions themselves. Assiduous photoprotection is critical; skin products including hydroquinone and retinoids and cosmeceuticals may give some minor improvement, however the most important factor is to find an effective treatment to prevent the development of further acne.