Red and brown marks after acne are not scars, and they are not the same thing. Medical Director Dr Sin Yong explains how to tell them apart and what helps each.
WhatsApp to Enquire →Key facts ↓PIE and PIH are flat marks left after acne, not scars. PIE is red or pink, from widened small blood vessels, and fades when pressed under a clear glass. PIH is brown, from extra pigment, and does not fade under pressure; it is more common and longer-lasting in Asian skin. Both improve with acne control and daily sunscreen; persistent marks need different lasers.
After a spot heals, it often leaves a flat mark. Two very different things cause most of them. Post-inflammatory erythema (PIE) is a red, pink or purplish mark made by small blood vessels that widened during the inflammation and have not yet settled. Post-inflammatory hyperpigmentation (PIH) is a brown or grey-brown mark made by extra melanin that pigment cells produced in response to the same inflammation.
A simple check separates them. Press a clear glass or the flat side of a clear plastic ruler firmly on the mark and look through it. If the colour fades while pressed, the mark is vascular, so it is PIE. If the colour stays, it is pigment, so it is PIH. Many people have both, sometimes in the same mark: a red centre with a brown rim, or red marks that turn brown as they fade.
Neither changes the contour of the skin. Run a finger over a mark, or look at it in side light: if the surface is level, it is a mark, not a scar. Dips and pits are scars, which are covered on acne scar treatment in Singapore.
| PIE (red marks) | PIH (brown marks) | |
|---|---|---|
| What causes the colour | Widened small blood vessels and lingering inflammation | Extra melanin in the epidermis, the dermis or both |
| Colour | Pink, red or purple | Light to dark brown, sometimes grey-brown |
| Glass (blanch) test | Fades when pressed | Stays when pressed |
| Who gets it most | Seen in every skin type; most visible in lighter skin | More frequent and longer-lasting in medium and darker skin, including most Asian skin |
| How long it lasts untreated | Often months; can persist longer | Months for surface pigment; a year or more for deeper pigment |
| Made worse by | Heat, picking, irritating skincare, sun | Sun and visible light, picking, irritation, harsh or heat-heavy treatments |
| What usually helps | Time, acne control, sun protection, barrier care; vascular-acting laser if it persists | Daily sunscreen, acne control, prescription or pigment-safe skincare, then pico laser, laser toning or peels if it persists |
| At IN Eternity Clinic | 少女光 675 nm laser for persistent redness | Pico laser, laser toning and chemical peels |
PIE is the redness of inflammation that has outstayed the spot. The small vessels in the upper dermis widened while the spot was active, and in some people they stay that way for months. It is most noticeable on fair skin, where redness shows readily, but it is common in Singapore too, especially after many inflamed spots in the same area.
Most PIE fades by itself once new spots stop forming. The process is helped by controlling acne, not picking, gentle barrier-friendly skincare and daily sunscreen, since sun keeps the vessels dilated. Where red marks persist, treatment aims at the vessels. At IN Eternity Clinic that is the 675 nm laser, delivered fractionally under contact cooling, which acts on the vascular component of the dermis. Elsewhere, pulsed dye laser and intense pulsed light are widely used for red marks; they are described here for comparison and are not the methods used at this clinic. Some topical treatments have also been studied for PIE and PIH together; whether any suits you is decided after assessment.
Resurfacing lasers are not a first choice for PIE. They add heat and inflammation to skin that is already red, and in Asian skin they can leave brown marks behind the red ones.
“Press a clear glass on the mark. If the colour fades, you are looking at blood vessels; if it stays, you are looking at pigment. The treatment follows that, not the word “scar”.”
PIH is the pigment response to inflammation. Inflammatory signals from the healing spot stimulate melanocytes, which make more melanin and pass it into the surrounding skin. When the extra pigment sits in the epidermis, the mark is mid-brown with a sharper edge and usually fades over months. When some of it drops into the dermis, the mark is greyer and more diffuse, and it can last a year or more, because there is no quick route out.
Studies of acne in Asian patients have found acne-related PIH in a large share of people, often lasting longer than the acne itself and sometimes bothering them more than the spots did. Even experts find it hard to grade consistently, which is why marks are photographed in the same light and judged over months rather than from week to week.
Treatment follows the cause first. While spots are still appearing, new PIH keeps forming, so acne control comes before pigment work. Then daily sunscreen that also blocks visible light, prescription or pigment-safe skincare where suitable, and, for marks that persist, gentle low-heat procedures such as pico laser, laser toning or superficial peels. In skin prone to PIH, an aggressive treatment can create the very problem it set out to fix. The clinical approach to PIH is set out on acne marks removal in Singapore.
A common reason people spend money on acne scar treatment without improvement is that they had marks, not scars, or both treated as one problem. Resurfacing lasers aimed at scars do little for PIE and can worsen PIH in darker skin; pigment lasers aimed at marks do nothing for a pitted scar.
| If you see | It is probably | Look at |
|---|---|---|
| Flat red or pink spots that fade under a glass | PIE | 675 nm laser, time and sun care |
| Flat brown spots that stay under a glass | PIH | Acne marks removal |
| Dips or pits that cast shadows in side light | Atrophic scars | Acne scar treatment |
| Firm raised bumps on the jaw, chest or shoulders | Hypertrophic or keloid scars | Keloid treatment |
The types of scars are explained on types of acne scars.
General clinical observations used at consultation; they describe what is checked, not any individual result.
Most flat marks after acne are PIE or PIH. A few need a different diagnosis.
Where any of these apply, the first step is a diagnosis.
PIE (post-inflammatory erythema) is a red or pink mark from widened small blood vessels; PIH (post-inflammatory hyperpigmentation) is a brown mark from extra melanin. Press a clear glass on the mark: PIE fades under pressure, PIH does not.
Most do, over months, once new spots stop forming. Sun protection, not picking and gentle skincare help. Red marks that persist can be treated with a laser that acts on the vessels.
Surface pigment often fades over a few months with daily sunscreen. Deeper, greyer pigment can last a year or more, which is when treatment is usually considered.
No. Marks are flat changes in colour; scars change the contour of the skin, as dips, pits or raised bumps. They are treated with different tools, and many people have both.
At IN Eternity Clinic, persistent red marks are treated with the 675 nm laser, which acts on the vascular part of the dermis. Pulsed dye laser and intense pulsed light are used elsewhere and are not the methods used at this clinic.
Daily sunscreen and acne control come first, then pigment-safe or prescription skincare. For marks that persist, gentle low-heat options such as pico laser, laser toning or superficial peels are used, with settings chosen to avoid causing more pigment.
The acne is treated first, because every new spot can leave a new mark. Sun protection and gentle skincare can start straight away, and some mark treatment can run alongside acne treatment once spots are under control.
IN Eternity Clinic, 9 Scotts Road, #12-01 Pacific Plaza, Singapore 228210. By appointment with Medical Director Dr Sin Yong. Monday to Saturday, 11am to 8pm. WhatsApp or call +65 8815 3008. The consultation fee is waived with any medical treatment.
These sources describe mechanisms and general evidence. They are not a promise of any individual result; suitability is decided at an in-person assessment.