When pigment looks darker after a laser: how I tell recovery from PIH
Skin looking darker after a pigment laser splits into two things. If fine crusting and a temporary shift in pigment are overlapping, it lightens between two and four weeks. If the border of the treated area spreads outward and nothing has changed at four weeks, it is closer to post-inflammatory hyperpigmentation (PIH). The first only needs time. The second means postponing the next session and lowering the energy.
Two or three weeks after starting pigment treatment, the sentence I hear most from patients coming back is, "Doctor, I had the laser and it looks darker than before." I bring out the photographs there and then and lay them over the pre-treatment ones, and it is almost always one of two things.
Telling recovery apart from post-inflammatory hyperpigmentation
After a laser the skin is irritated, and existing pigment can look briefly darker. Fine crusts settle and read as dark patches. In that case the border of the treated area stays fairly sharp, and as the crusts come away between two and four weeks the colour lightens with them.
Post-inflammatory hyperpigmentation has a different shape. The border of the treated mark widens as if bleeding outwards, and the colour tends towards grey-brown rather than plain brown. If it is unchanged at four weeks, or wider than before, I read it as PIH. Going "it did not clear, so let us go stronger" from here only repeats the same thing.
So during pigment treatment I photograph under the same light at the same angle every visit. An impression a month later that the skin looks darker cannot separate the two.
Why the depth of the pigment changes the response
Two browns that look identical behave differently depending on whether the pigment sits shallow in the epidermis or straddles the basement membrane at the junction with the dermis. Shallow pigment lightens visibly within a few sessions. Pigment formed where the basement membrane is already disturbed does not clear even when I raise the energy, and it returns as post-inflammatory pigmentation in proportion to how hard I pushed.
That is what I presented at a 2019 spring conference of the Korean laser dermatology and hair society, approaching stubborn pigmentary conditions from the basement membrane. Reading pigment that will not clear as nothing more than a laser that was too weak sets every decision after it in one direction.
When I postpone the next session
Pigment treatment looks like a programme with fixed intervals, but I decide on the day in front of the skin. If any one of the following applies, I do not use the laser that day. I switch to moisturising and sun protection and see you again in two weeks.
| What I check that day | If it applies |
|---|---|
| The border of the treated mark is wider than last time | The next session is postponed and the energy comes down |
| The area still stings or burns to the touch | Calming the skin comes first |
| A lot of time outdoors in the past two weeks | Skin responds differently after UV exposure |
| A brightening product or exfoliation started recently | I work out what caused it before going on |
The other way round, if the pigment is shallow and recovery is going well, I do not stretch the interval for the sake of it. I do not fix one rule and apply it to everyone. If you are flying in for a short stay, tell me your dates at the first visit. Whether a second session fits into this trip is decided by how the first one settles, not by the calendar.
The two weeks after a laser that change the result more than the laser
In 2018 I lectured at a Korean aesthetic dermatologic surgery society under the title "Post-laser care matters more than the laser". The title sounds like an overstatement, but with pigment it holds. The same device on the same settings gives a different result depending on how the following two weeks go.
- Sun protection: exposure continues on cloudy days and indoors by a window. During pigment treatment, how often you reapply matters more than which product you bought.
- No rubbing: the force of a hand passing over the face while cleansing is enough to irritate skin that has only just settled.
- Leave the crusts alone: pull one off and that spot stays the longest.
- No new products: for two weeks after treatment, use only what you were already using.
FAQ
How many days does the darkening after a laser last?
When it is part of recovery it usually lightens between two and four weeks. If nothing has changed at four weeks, or the border has spread further, it may be post-inflammatory hyperpigmentation, and it is safer to have it checked before the next session.
If the pigment is not clearing, do I need a stronger laser?
I check the type and the depth first. Pigment straddling the basement membrane comes back as post-inflammatory pigmentation the harder you push. More often I adjust the interval and the aftercare rather than the energy.
Can I use brightening products right after a laser?
For the first two weeks keep to what you were already using. Adding something new makes it impossible to tell whether a reaction came from the laser or from the product.
Is summer a bad time for a pigment laser?
I look at your actual UV exposure and your sun protection habits rather than the season. If you are outdoors a great deal, I lower the energy and lengthen the interval, or move the schedule to a time when exposure drops.
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