Why Are Some People More Prone to Post-Acne Pigmentation?

Dr Cheong Wai Kwong
Senior Consultant Dermatologist
MBBS (Singapore), MRCP (UK), FRCP (Edinburgh), FAMS (Dermatology)

Two people can experience similar acne breakouts yet be left with very different marks once their spots heal. For some, the skin gradually returns to its usual colour. For others, flat brown, grey or dark patches remain for months.

These marks are commonly known as post-inflammatory hyperpigmentation (PIH). They develop when inflammation from acne stimulates the skin to produce excess melanin, the pigment responsible for skin colour. While PIH can affect anyone, it tends to be more noticeable and persistent in people with darker skin tones.

The likelihood and severity of post-acne pigmentation depend on several factors, including skin type, the intensity of inflammation, sun exposure and how the breakout is managed. Understanding these differences can help explain why your skin may develop pigmentation even when someone else's does not.

Which Skin Types Are More Prone to Post-Acne Pigmentation?

PIH can develop in all skin tones, but people with medium to darker skin are generally more susceptible. Research consistently finds that PIH is more common and can persist for longer in darker skin phototypes.

Dermatologists sometimes describe skin using the Fitzpatrick skin phototype scale, which ranges from Type I to Type VI according to how skin typically responds to ultraviolet (UV) exposure.

• Fitzpatrick Types I and II: People with lighter skin may be more likely to notice lingering red or pink marks after acne. These are not necessarily caused by excess melanin and may instead be post-inflammatory erythema, which is associated with changes in superficial blood vessels.
• Fitzpatrick Types III and IV: These phototypes are commonly seen among people with medium skin tones, including many Asian individuals. Post-acne inflammation may leave brown or grey marks that remain visible after the original breakout has healed.
• Fitzpatrick Types V and VI: People with darker skin phototypes are generally more susceptible to PIH, and the resulting pigmentation may be more persistent. However, the extent of discolouration still varies according to the inflammatory response and other individual factors.

Skin tone alone, however, does not determine whether pigmentation will develop. Two people with a similar skin tone can still respond differently to comparable breakouts.

How Do Sun Exposure and Singapore's Climate Affect Post-Acne Marks?

UV radiation can stimulate melanin production, which may make existing PIH darker or more persistent. Visible light may also contribute to pigmentation, particularly in darker skin phototypes.

This is particularly relevant in Singapore, where sun exposure occurs throughout the year. Consistent sun protection can therefore form an important part of managing skin that is prone to post-acne pigmentation.

Heat and humidity do not directly cause PIH, but they may influence skin oiliness, sweating and skincare habits. For people prone to acne, ongoing breakouts can lead to repeated inflammation, increasing the likelihood of developing new pigmented marks.