You are right, the red/brown post-acne marks are called Post-inflammatory hyperpigmentation (brown marks) and Post-inflammatory Erythema (red marks). These post-acne marks are formed due to the inflammation and injury to your skin after acne.
Treatment for Post-Inflammatory Erythema
For Post-Acne Red Marks (Post-inflammatory Erythema), Vascular lasers are the best type of lasers to treat these red marks. Vascular Lasers target the haemoglobin in your blood vessels to reduce redness over several treatment sessions (>5 sessions). Examples of vascular lasers include V Beam, Excel V, Pro Yellow and Gold Toning Lasers.
Treatment for Post-Inflammatory Hyper-pigmentation
For Post-Acne Brown Marks (Post-inflammatory Hyperpigmentation), Pico Lasers such as PicoPlus, PicoSure and Discovery Pico lasers are good lasers to remove the excess pigmentation. Similarly, several treatment sessions (>5 sessions) are required to fade the marks. Each pico laser session can be spaced 2-3 weeks apart.
Apart from Lasers, Topical Retinoid creams such as Differin and Tretinoin will help to lighten these post-acne marks. Chemical peels also increase cell turnover and help to lighten these post-acne marks faster.
Apart from these clinic-based/medical treatments, I highly suggest regular and adequate Sun protection to prevent worsening of your post-acne marks.
You might want to check out these articles for more information on the Best Acne Scar Treatments in Singapore and the Cost of Acne Scar Treatments in Singapore.
