Pico laser or Q-switched laser for pigment, and which suits your skin

What differs between a pico laser and a Q-switched laser

What sets the two classes apart is how long each pulse of light lasts. A Q-switched laser fires pulses measured in nanoseconds, or billionths of a second, and a 2023 melasma trial calls it the nanosecond Q-switched laser. A picosecond laser, usually called a pico laser, fires pulses measured in picoseconds, or trillionths of a second.

The two classes arrived at different times. As a 2017 tattoo trial reports, nanosecond lasers have been used to remove tattoos for decades, and picosecond lasers have been available for tattoo removal since 2012. Both are now used on pigment the body makes, such as sun spots and melasma, as well as on tattoo ink.

“Q-switch lasers are a long-standing option for treating pigmentation like sunspots and melasma.” Dr Samantha Tay

This article gives no figure for how many times shorter one pulse is than the other, because we found no primary source for a single figure that holds across machines. The clinic's page on pico laser treatment covers how its own sessions run.

What laser toning means, and why it can be done with either laser

The word toning appears on treatment menus and in research papers, and it is easy to read it as a third kind of laser. It is not. Toning describes a way of using a laser at low energy, and the research uses it with both classes. A 2022 split-face trial set picosecond toning against Q-switched toning, both at 1,064 nm, in 20 people with melasma. One side of each face was treated with each laser. The trial found no significant difference in melasma scores between the two.

What three trials found for sun spots and deeper marks such as nevus of Ota

Pigment does not all lie at the same level of the skin. Sun spots, which doctors call solar lentigines, are a benign, non-cancerous kind of pigment in the epidermis, the outer layer of the skin. That is how a 2020 sun spot trial describes them. In that trial, 20 people had a 532 nm picosecond laser on one half of the face and a 532 nm Q-switched laser on the other.

Three blinded dermatologists scored greater clearance on the picosecond side. Darkening after treatment followed 5% of picosecond sides and 30% of Q-switched sides, while satisfaction and pain did not differ significantly between the two.

Marks that look like nevus of Ota sit deeper, in the dermis. A 2020 trial of epidermal and dermal pigment treated 14 people, 8 with lentigines and 6 with marks resembling nevus of Ota. Each had a picosecond laser on one half of the face and a Q-switched laser on the other. At the final assessment, 85.7% of picosecond sites and 57.2% of Q-switched sites showed more than 50% improvement. Side effects and healing time did not differ significantly, and discomfort was lower on the picosecond side.

The third, a 2020 trial of 56 people with nevus of Ota, split each mark in two. One half had a picosecond alexandrite laser and the other a Q-switched alexandrite laser. The picosecond half scored 4.53 for clearance on a 5-point scale, against 4.0 for the Q-switched half. Pain scored 5.61 against 6.40. Darkening after treatment was seen in 26% against 34%, and pale patches in 21% against 47%. The authors list the lack of objective measurements as a limitation.

Why melasma needs a slower plan with a pico laser or Q-switched laser

Melasma can be controlled rather than cured, and it can come back after either laser, so it gets a slower plan whichever laser is used. The clinic's melasma treatment article sets out that plan, from sun protection and creams to lasers. The clinic's pico laser page gives four to eight sessions for stable melasma, and says the response varies and that melasma often returns without daily sun protection.

Four melasma trials described here set the two lasers side by side. In a 2018 trial of 12 people, one side of each face had a 755 nm picosecond laser and the other a 1,064 nm Q-switched laser. The picosecond side showed greater clearance. The 2022 toning trial above found no significant difference, and so did the 2023 trial of 18 people. That trial found the Q-switched side more painful and the same recurrence rate, 12.5%, on both sides.

The fourth, a 2024 trial with two years of follow-up, had 20 people, 3 of whom dropped out. It set a 755 nm picosecond laser fitted with a lens array against a 1,064 nm Q-switched laser. Melasma scores fell significantly from baseline on the Q-switched side and not on the picosecond side, yet the two sides did not differ significantly from each other. The Q-switched side was less painful. Ten people, 58.82% of those followed, reported the melasma returning or worsening at two years, with no significant difference between the lasers.

The 2018 and 2024 trials used the same two wavelengths and came out differently. The 2024 trial fitted the picosecond laser with a lens array, which the 2018 trial's summary does not mention. The two trials differed in other ways too, so they cannot say which difference mattered. What they do show is that the same two wavelengths can give different answers.

Tattoo removal with a pico laser or Q-switched laser is a separate question

Tattoo ink comes from outside the body, unlike sun spots or melasma, so tattoo removal is a separate question. In the 2017 trial of 21 people with 30 black tattoos, with both lasers at 1,064 nm, clearance did not differ significantly. Pain scored 3.8 with the picosecond laser against 7.9 with the nanosecond laser, on a scale of 0 to 10.

A 2022 trial of 23 people with 30 black or coloured tattoos set a picosecond laser at 532 and 1,064 nm against a nanosecond laser at 694 nm. Clearance did not differ significantly, and pain was significantly lower with the picosecond laser. Darkening followed both lasers, pale patches followed the nanosecond laser alone, and the study saw no scarring with either.

Nexus offers tattoo removal with its picosecond laser, over several sessions.

What the nine trials add up to, and what they cannot tell you

Put together, the nine head-to-head trials described here each had between 12 and 56 people. The picosecond side showed greater clearance in all three trials of sun spots and nevus of Ota and in one of the four melasma trials. The other five, three on melasma and two on tattoos, found no significant difference. On pain, five trials reported the picosecond side as less painful and one reported the Q-switched side as less painful. One found no difference, and the summaries of the other two give no clear pain result.

A 2025 pooled analysis combined 20 randomised trials and one retrospective comparison, 971 people in all. For pigment made by the body itself, it found comparable clearance (a risk ratio of 1.06, 95% confidence interval 0.85 to 1.31, where 1 means no difference). For tattoo pigment, it found a trend toward greater clearance with picosecond lasers (1.39, 95% confidence interval 0.99 to 1.94, P = 0.05). It also found less pain and fewer cases of post-inflammatory darkening with picosecond lasers. The authors write that this safety profile is supported mainly by studies in Asian patients, and that data remain sparse for other skin types.

These studies cannot say that one class suits every person. Each used particular machines, wavelengths and settings. Apart from one two-year melasma trial, the trials followed people for weeks to months, and the pooled analysis mixed conditions. Where the studies do not separate the two classes, the table below gives the same entry for both.

What can leave skin darker or paler after either laser

Darkening after treatment, which doctors call post-inflammatory hyperpigmentation, and pale patches, called hypopigmentation, have been reported after both kinds of laser. The table shows where each was seen in the trials above.

Redness and swelling can be part of the treatment itself. In the 2018 melasma trial, doctors treated each side, with either laser, until mild redness and swelling appeared, stopping short of pinpoint bleeding spots. The doctor chooses the settings and how often sessions are repeated for your skin, which is why the questions further down are worth asking.

The clinic's pico laser aftercare guide covers what to do and what to avoid after a session.

How a doctor chooses the laser, the settings and the number of sessions

The trials above differed in the kind of pigment, the wavelength and the way the laser was fitted, and their answers differed too. Speaking of the pico laser, Dr Samantha puts it this way.

“The number of sessions needed and the treatment protocol or settings that we're gonna use will vary based on the individual and the condition that we're treating.” Dr Samantha Tay

At the first visit, the doctor looks at what kind of pigment it is before suggesting a laser, a setting or something else. You can read how the clinic plans pico laser for pigmentation on its treatment page.

Some people wait before a pico laser at Nexus: anyone who is pregnant or breastfeeding, and anyone taking a medicine that makes the skin more sensitive to light. A history of cold sores is worth raising first, as treatment can bring them back.

What else can treat pigment, with or without a laser

A laser is one option among several, and which one fits depends on the kind of pigment. The clinic's pigmentation treatment article explains how the clinic tells sun spots, melasma and marks left by acne apart, and how each is treated.

What to ask before a pico laser or Q-switched laser, and what to bring

A consultation should leave you knowing why one laser, one setting or no laser was chosen for your skin. These questions work with any doctor, and the second list helps the doctor answer them.

The research does not point to one of these lasers for every person. The kind of pigment, your skin and how the laser is set decide what fits. The choice is made at a consultation, after the doctor has examined you and looked at what kind of pigment it is.