Laser Hair Removal Side Effects: What’s Normal, What’s Rare
The short answer
Most laser hair removal side effects are mild and short-lived: skin that feels warm like a mild sunburn, looks pink, and shows small raised bumps around the treated follicles. They usually settle within a few hours. Less common are acne-like spots and temporary darker or lighter patches. Blistering, burns, lasting pigment change and scarring are rare, and when they happen the cause is usually avoidable: a recent tan, settings too strong for the skin, or a skipped patch test.
So is laser hair removal safe? A review of the published research concluded that, carried out by trained professionals, it is a safe procedure with a very low incidence of permanent effects. Safe is not the same as risk-free, though, and the rest of this guide is about the difference: what is normal, what is not, and what you can do about the second list before you book.
Side effects at a glance
Grouped by how often they happen. The first column is the treatment working; the last is what good practice exists to prevent.
- ExpectedMost people, most sessions
- Warmth and pinknessSettles within a few hours
- Small bumps around folliclesSame day; next day on coarse areas
- Itching as treated hairs shedOver the following one to three weeks
- UncommonSome people, usually brief
- Acne-like spots6% in one multi-centre study; mostly mild
- Darker or lighter patchesMore likely with a tan or deeper skin; usually fade
- Cold sore flare-upOnly near the lips, in people who get them
- Extra hair growth nearbyAbout 3%, almost all on the face and neck
- RareAvoidable with good practice
- Blisters and burnsSettings too high, a tan, poor cooling
- Lasting pigment change or scarringUsually follows a burn
- Changes to tattoos or molesWhen they are treated over
- Eye injuryWithout eyewear rated for the laser
The normal ones: what most people notice
Warmth and pinkness. The laser deliberately heats each follicle, and the skin around it responds the way it would to mild sun: warm, pink, sometimes a little tender. It usually settles within a few hours.
Small raised bumps. Little bumps around individual follicles, called perifollicular oedema, are the reaction that alarms people most and the clearest sign the energy reached the follicle rather than just warming the skin. On coarser areas such as the underarms and bikini line they can last into the next day. They are a short-lived reaction to treatment, not the same as strawberry legs, the dark dots that shaving can leave behind.
Itching and shedding. Over the following one to three weeks, treated hairs work their way out of the follicle. It can itch a little, and it looks like regrowth. It is not.
A cool compress, loose clothing, and no heat, sweat or sun on the area for 48 hours cover almost all of it. Our laser hair removal aftercare guide goes through it hour by hour.
The less common ones
Acne-like spots. A multi-centre study that tracked this specifically found acne-like reactions in 6% of patients, more often in younger clients, and in most cases mild and short-lived. Keep the area clean, skip heavy sweating for the first 48 hours, and do not pick. These are not the same as ingrown hairs, which have a different cause.
Darker or lighter patches. When skin is irritated it can lay down extra pigment, or occasionally lose some. This is the side effect most tied to skin tone and to the laser itself: the same 2006 review found pigment changes in up to 19% with shorter-wavelength lasers, particularly on darker skin, against 2 to 3% with the long-wavelength Nd:YAG laser. Longer wavelengths reduce the risk in darker skin, which is why the FEMME 4D includes 1064 nm. Patches usually fade, but over weeks to months rather than days, and sun on the area slows that down. Our guide to laser hair removal on dark skin explains the wavelength question in full.
Cold sores. Health Canada lists cold sore outbreaks among the side effects. If you get them and the lips or chin are being treated, say so beforehand; some people take an antiviral first on the advice of their own healthcare provider.
The rare ones, and why they happen
Blisters and burns. These come from too much energy reaching the skin instead of the follicle: settings too strong for the skin type, treating over a tan, poor cooling, or overlapping pulses on the same spot. Skin that blisters, or turns white or grey during treatment, is not a normal reaction and is worth a call the same day.
Lasting pigment change and scarring. Health Canada describes permanent pigment change and scarring as rare, and both usually follow a burn rather than appearing on their own. Preventing the burn is preventing these.
Tattoos, permanent makeup and moles. Ink and dark moles absorb laser energy just as hair does, and Health Canada lists changes to tattoos, freckles and moles among the possible effects. They should be worked around, not treated over. A mole you are already watching is worth raising at your consultation, which our post on laser hair removal and cancer covers.
Eye injury. This is why everyone in the room wears eyewear rated for the laser’s wavelength. Health Canada is blunt that ordinary safety glasses are not laser protection, and that a laser injury to the retina cannot be repaired. Laser is not used on the eyelids.
Paradoxical hypertrichosis: when hair grows back thicker
The strangest side effect of all is hair growing more: finer hairs near a treated area turning darker and coarser. It is called paradoxical hypertrichosis, and it is the one people are least likely to have been warned about.
How often extra hair growth happens
A 2021 meta-analysis pooled 22 studies covering 9,733 patients treated with laser or light.
Two findings matter more than the headline figure. It is almost entirely a face and neck reaction, and in three of the four studies that tracked it, it gradually improved as treatment continued. The authors suggest continuing treatment as the most appropriate response. If you notice new growth close to a treated area, tell your technician rather than stopping on your own. It is a different thing from hormonal regrowth, which our PCOS guide explains.
Long-term side effects: what the evidence says
The worry behind most searches for long-term side effects is cancer or fertility. Laser hair removal uses non-ionising light that does not reach beyond the skin, and there is no established link to either; we cover the evidence in does laser hair removal cause cancer and does laser hair removal lead to infertility. On the skin itself, the two largest studies in the 2006 review found no long-term side effects or scarring. The one firm line we draw is pregnancy, which we explain in laser hair removal while pregnant.
Check your own risk factors
Most of what raises the risk is known before the first pulse. Tick anything that applies to the area you want treated.
Before you book
Nothing here is sent anywhere. It sorts what you tick into what to wait for, what to mention, and what simply needs extra care.
What a careful clinic does before the first pulse
Nearly every rare side effect on this page traces back to a step that was skipped. Whichever clinic you choose, these should happen:
- A skin assessment on the Fitzpatrick scale, and questions about your medical history and medications.
- A patch test at the settings they intend to use, with a wait of days, not minutes, before the full session.
- A wavelength suited to your skin, including 1064 nm for deeper tones.
- Contact cooling on the skin as each pulse fires.
- Eyewear rated for the laser, for you and for the technician.
- Tattoos and moles worked around, and pulses that do not overlap on the same spot.
- Written aftercare, and a number to call if something does not look right.
At Femme, every course starts with a Fitzpatrick assessment and a patch test, the FEMME 4D’s sapphire tip is chilled to around −5 °C against the skin as it fires, and you wear protective eyewear throughout. More on how a session runs is in our laser hair removal guide, and on what it feels like in does laser hair removal hurt.
When to call the clinic
Most reactions settle on their own. These do not, and are worth a call rather than a wait:
- Blistering, or skin that stayed white or grey after treatment.
- Pain that is still there the next day, rather than warmth that faded within hours.
- Redness that spreads beyond the treated area, or feels hot to the touch.
- Pus, or a rash that worsens over 48 hours rather than settling.
- A dark or light patch appearing in the treated area in the weeks afterwards.
- Any change in your vision after a session, which needs prompt medical attention.
Questions we hear about side effects
What are the most common side effects of laser hair removal?
Warmth and pinkness like a mild sunburn, and small raised bumps around the treated follicles. Both usually settle within a few hours, or by the next day on coarser areas such as the underarms and bikini line. Mild itching a few days later, as treated hairs shed, is also normal.
How long do laser hair removal side effects last?
Redness and bumps usually settle within a few hours and occasionally last into the next day. Acne-like spots, when they happen, are usually mild and brief. A darker or lighter patch can take weeks to months to fade, which is why sun protection between sessions matters.
Is laser hair removal safe?
For most people, yes. A review of the published research found adverse effects uncommon and permanent ones very rare when trained professionals carry out the treatment. It is not risk-free: a recent tan, settings too strong for your skin or a skipped patch test are what raise the risk.
Can laser hair removal burn your skin?
It can, but it should not. Burns and blisters usually come from energy set too high for the skin, treating over a tan, poor cooling or overlapping pulses. A skin assessment, a patch test and settings chosen for your skin are the safeguards. Blistering is always worth a call to the clinic.
Can laser hair removal make hair grow thicker?
Rarely. It is called paradoxical hypertrichosis. A 2021 analysis of 9,733 patients put it at about 3 percent, almost entirely on the face and neck, and in three of the four studies that tracked it, it improved as treatment continued. Tell your technician if you notice new growth near a treated area.
Does laser hair removal have long-term side effects?
Lasting effects are very rare. The two largest studies in a 2006 review found no long-term side effects or scarring. Laser hair removal uses non-ionising light that does not reach beyond the skin, and there is no established link to cancer or infertility.
Is laser hair removal safe on the face?
Yes, with two extra points. The face and neck are where paradoxical hair growth is most often reported, and treating near the lips can trigger a cold sore if you get them, so mention it beforehand. Laser is not used on the eyelids, and you wear eye protection throughout.
Start with your skin, not the laser. A free consultation covers your skin assessment, medications and a patch test, and we will tell you plainly if anything means waiting, or if laser is not the right choice for you.
Book a consultationPrefer to talk first? Call 647-229-7397. If you are planning a course, see how many sessions you will need and our preparation guide.
Sources: Lim SP, Lanigan SW. A review of the adverse effects of laser hair removal. Lasers in Medical Science 21, 2006. Carter JJ, Lanigan SW. Incidence of acneform reactions after laser hair removal. Lasers in Medical Science 21, 2006. Snast I, Kaftory R, Lapidoth M, Levi A. Paradoxical hypertrichosis associated with laser and light therapy for hair removal: a systematic review and meta-analysis. American Journal of Clinical Dermatology 22, 2021. Health Canada. Laser Hair Removal: Safety Guidelines for Facility Owners and Operators, 2011.
