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Why does acne leave dark spot?

This is a condition known as postinflammatory hyperpigmentation (PIH). “Post” means after, and postinflammatory hyperpigmentation simply means hyperpigmentation after inflammation, commonly from acne, impetigo, eczema, bug bites, rashes etc.

Melanin is natural pigment that gives colour in your hair, skin, and eyes. After inflammation or injury, your skin produce extra melanin, and melanin may deposit abnormally, resulting in hyperpigmentation. PIH can affect either your epidermis (skin’s surface level), your dermis (deep layer of your skin) or mixed. The lesions range from light brown to black in colour. It can occur in anyone, but is more common and longer lasting in individual with medium to dark complexions as people with skin of colour has more melanin. Similarly, people with oily skin often develop more severe, resistant PIH because sebum is a pro-inflammatory substance.

PIH fades over time, but it can take months to years to fully clear. So, treatment can be done to speed up the process.

How do we treat it?


Daily use of broad-spectrum SPF 30+ sunscreen is essential to minimize darkening caused by UV ray.

A variety of topical agents are available to lighten dark spot, namely:

- Kojic acid

- Arbutin

- Niacinamide

- Licorice extract

- Hydroquinone

- Retinoids

- Glycolic acid

- Azelaic acid

- Corticosteroids

- Vitamin C

*long term use of hydroquinone can cause exogenous ochronosis, which is paradoxical hyperpigmentation of skin, characterized by blue-black discolouration. So, keep use less than 10 weeks and reuse after 3 months to minimise the risk of ochronosis.

Lightening of PIH may be achieved with previously named topical agents. If fails to respond to topical products, or PIH involves deeper layer of your skin, combination with physical treatment like chemical peel or laser are required for significant improvement.


Chemical peel is a simple yet effective way to treat PIH. It involves application of chemical agent on your skin resulting in exfoliation of skin affected by PIH, followed by regrowth of new skin with improved appearance and texture. Getting rid of oil and dead skin cells by chemical peel also keep your pores clear, which means less blockage and less acne!


Laser toning with our 1064nm Q-switched Nd:YAG laser is able to treat pigments located deeper in the skin, thus is effective for deeper PIH. Laser toning uses lower fluence shot in multiple intervals. It does not leave scab as treatment occurs deep within the skin, and has no downtime.


PIH can appear on sun-exposed or sun protected skin, but UV ray usually worsens PIH. To prevent further darkening of lesions and new ones from forming, avoid the sun whenever possible, or use umbrella, wear protective clothing, cap/ hat to reduce sun exposure. Sunscreen should also be applied on daily basis.

Last but not least, TREAT ITS CAUSE. No inflammation= no PIH.

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