A post-inflammatory hyperpigmentation macule is often left behind as the result of an inflamed acne lesion.
PIH macules can appear from fairly insignificant papules or pimples right up to more serious wounds. That said, the more inflammation there is, the more obvious the PIH macule will be, both in terms of size and colour. If a pimple is squeezed or picked it will increase the chance of developing post-inflammatory hyperpigmentation.
Whilst not the cause of PIH, the sun can aggravate the symptoms, darkening the affected patches and prolonging the time it can take for them to fade.
Post-inflammatory hyperpigmentation does not cause scarring and, even with no treatment, it will improve over time. Recovery rates vary but, on average, it can take anything from three to 24 months for the darkened areas to fade. Although in some cases it may take longer. The timing depends on the difference in skin tone between the natural skin tone and the darkened patches - the more significant the difference, the longer it will take for the tones to rebalance. Treatments are available that can improve and speed up this recovery time.