Hair Removal

Permanent hair removal: seven reasons and one caveat

A laser only destroys a follicle whose hair is in its growth phase, and on most body areas that is just 20 to 30% of the hairs on any given day, so a series of 6 to 10 sessions at intervals of 4 to 8 weeks is normal. Each session removes roughly 10 to 25% of the hair, the result is a lasting reduction rather than complete removal, and it works on dark hair only. Seven points speak for it; one caveat belongs in every consultation and tends to be mentioned last.

Why one session is never enough

Every hair passes through three phases: growth, which lasts months to years, a transition of 2 to 3 weeks, and a rest of roughly 3 months before the hair falls out and the follicle starts again. The laser relies on selective photothermolysis: pulses of light between about 600 and 1,200 nanometres are absorbed by melanin in the hair shaft, which heats up and passes the heat to the cells around the root. That only works while the shaft sits in an active follicle, so a resting hair is out of reach on the day, whatever the device.

How many hairs are growing at the same time depends on the body area. On the legs it is about 1 in 5, in the armpits and bikini line around 1 in 3, on the upper lip closer to 2 in 3. Those proportions set the count: the American Academy of Dermatology gives 2 to 6 treatments for most patients, while hormonally driven areas such as the face and bikini line more often need 8 to 10. The interval, 4 to 6 weeks on the face and 6 to 8 weeks on legs and back, follows the cycle of that region, not the diary of the practice. After the first session expect 10 to 25% less hair; what returns comes in finer and lighter.

Seven reasons that speak for the laser

1. It lasts. After a full series most people stay free of visible hair for months to years. In the Cochrane review of 11 randomised trials with 444 participants, alexandrite and diode lasers achieved a reduction of about 50% measured 6 months after treatment; apart from electrolysis, no other method comes close.

2. It is quick per area. An upper lip takes 5 to 10 minutes, the armpits 10 to 15, full legs 45 to 90 minutes. Against the 20 to 40 minutes a leg wax needs every 4 weeks for life, the hours add up in favour of the laser.

3. Fewer ingrown hairs. Because the follicle is weakened rather than the hair torn out, the laser is a recognised treatment for razor bumps (pseudofolliculitis barbae) on the beard, neck and bikini line.

4. No downtime. Redness and swelling around the follicles look like a mild sunburn and settle within 1 to 3 days; most people go straight back to work.

5. The maths works over years. A series of 6 to 8 sessions costs roughly 300 to 700 EUR for the armpits and 1,200 to 2,500 EUR for full legs, depending on country and device. Waxing the same legs every 4 weeks at 30 to 60 EUR a visit comes to 400 to 800 EUR a year, with no end date.

6. It suits almost every skin type today. The ruby lasers of the 1990s were safe on pale skin only; diode lasers at 810 nanometres and the Nd:YAG at 1,064 nanometres reach the follicle past the pigment of brown and black skin, so skin types I to VI can be treated, provided device and settings match.

7. Side effects are rare and mostly avoidable. Burns, blisters and pigment changes appear almost exclusively when the wrong wavelength or energy meets tanned or dark skin, or when the operator lacks training. Kept out of the sun for 4 weeks either side of a session, the skin rarely reacts with more than a day of redness.

The caveat about pigment and permanence

The honest term is permanent hair reduction. Even the well-studied alexandrite and diode lasers leave follicles that recover, and the Cochrane authors found no trial documenting complete long-term removal, which is why most clinics schedule a maintenance session every 6 to 12 months. Electrolysis is the only method that regulators in the United States allow to call itself permanent hair removal, and it works one hair at a time; our comparison of hair removal methods sets the two side by side.

The second limit is pigment. White, grey, red and very light blonde hair contain too little melanin to absorb the energy, and no wavelength changes that. With dark skin and dark hair the skin competes for the light: ruby and alexandrite lasers are safe for skin types I to III, the diode up to type V, the Nd:YAG for all six, at the price of slightly lower absorption by the hair. Intense pulsed light, a broadband flash between 500 and 1,200 nanometres, is cheaper per device and slower in effect, and the Cochrane review found little evidence for it.

The third limit is hormonal. Hair on the chin, jaw or lower abdomen that answers to androgens, as in polycystic ovary syndrome, grows back sooner because the stimulus continues. In a few patients light treatment even provokes the opposite of what it should: paradoxical hypertrichosis, fine hair turning dark and coarse around the treated field, reported most often in skin type III and with IPL devices. If facial hair appeared within the last 1 to 2 years or comes with irregular periods, read our guide on female facial hair and see a doctor first.

Who may hold the handpiece

A hair removal laser is a Class 4 device, with an output above 500 milliwatts that can burn skin and injure an eye in a fraction of a second; some are built as Class 1C products, where the housing prevents eye exposure while the beam on the skin stays at Class 4 level. Who may operate one differs by country. Germany brought laser and IPL hair removal under a radiation protection regulation in 2020 and requires a certificate of competence from every operator; the United Kingdom classes such devices as unsuitable for consumer use; and the EU has applied common safety specifications for medical devices to these lasers and IPL devices since 22 June 2023. The American Academy of Dermatology recommends a board-certified dermatologist or treatment under one's direct supervision, because burns, permanent colour changes and scars occur in inexperienced hands.

Whatever the local rule, the questions are the same. Ask for the training certificate and how many treatments the operator has done on your skin type, which device and wavelength will be used and why, and what cooling (contact plate, cold air or cryogen spray) protects the surface while the follicle heats. Ask for a test patch of a few square centimetres 1 to 2 weeks before the first full session. Moles, tattoos and permanent make-up in the field must be covered or left out, because their pigment absorbs the light just as hair does, and everyone in the room wears eyewear rated for the wavelength for the whole session.

Before and after a session

The follicle must still be there for the laser to find it, so no waxing, plucking, threading or epilating for 6 weeks before a session. Shaving is fine and is in fact required 1 to 2 days beforehand, leaving a short stubble that takes the energy without scorching the surface. Tanned skin is the commonest cause of burns and pigment marks, so stay out of the sun and off sunbeds for 4 weeks before each appointment, wear SPF 30 to 50 on exposed areas in the 4 to 6 weeks before, and skip self-tan for 2 weeks. Tell the practice about medication: photosensitising antibiotics, St John's wort and retinoids matter, and many clinics wait 6 months after isotretinoin. A history of cold sores calls for antiviral tablets before a lip treatment; a numbing cream goes on 30 to 60 minutes before, on a small area only.

The pulses feel like a rubber band snapped against the skin, and the area is red and slightly swollen afterwards. A cool compress in the first hours, a bland moisturiser and no hot baths, saunas or sport for 24 to 48 hours are usually enough. Keep the area covered or under SPF 30 to 50 for 4 weeks, because inflamed skin pigments faster under UV, and leave the treated hairs that push out over the following 1 to 3 weeks alone: they are dead and shed on their own. Blisters, crusts or a patch that stays darker or lighter after 2 weeks belong in front of the practitioner and, if they persist, a dermatologist.

Questions to ask before you book

Frequently asked

Why do I need so many sessions?

Because the laser only reaches hair in its growth phase, and depending on the area that is 20 to 65% of the hairs at any moment. Each session removes roughly 10 to 25% of the hair, so a series of 6 to 10 sessions at 4 to 8 week intervals is the norm.

Does laser hair removal work on blonde, grey or white hair?

No. Those hairs contain too little melanin to absorb the light, whatever the device. Electrolysis, which destroys the follicle with a fine probe one hair at a time, is the alternative.

Is the result really permanent?

The correct term is permanent hair reduction. Alexandrite and diode lasers reduce hair by about 50% at 6 months after treatment in randomised trials, some hair returns over the years, usually finer and lighter, and a maintenance session every 6 to 12 months is common.

Can I go in the sun before or after a treatment?

Not for 4 weeks on either side. Tanned skin absorbs the energy meant for the hair, which is the main cause of burns and pigment changes; use SPF 30 to 50 on exposed areas between sessions.

Does it hurt?

Each pulse feels like a rubber band snapped against the skin, and the cooling on the handpiece takes most of the sting. A numbing cream applied 30 to 60 minutes before helps on sensitive areas, and the redness afterwards settles in 1 to 3 days.

Who is allowed to do it?

That depends on the country. Germany requires a certificate of competence for laser and IPL hair removal, the EU has applied common safety specifications for these devices since June 2023, and dermatology associations recommend treatment by or under the supervision of a dermatologist. Ask for the certificate and a test patch.

Sources

• American Academy of Dermatology: Laser hair removal, FAQs · 10 to 25% reduction after the first treatment, 2 to 6 treatments at 4 to 6 week intervals, side effects settle in 1 to 3 days, numbing gel 30 to 60 minutes, sun avoidance, board-certified dermatologist
• Vaidya T, Hohman MH, Kumar D: Laser Hair Removal, StatPearls, NIH National Library of Medicine, updated 2023 · selective photothermolysis, wavelengths 600 to 1,200 nm, devices by Fitzpatrick skin type, 4 to 6 sessions minimum, maintenance every 6 to 12 months, no waxing for 6 weeks before, paradoxical hypertrichosis
• Haedersdal M, Gøtzsche PC: Laser and photoepilation for unwanted hair growth, Cochrane Database of Systematic Reviews 2006 · 11 randomised trials, 444 participants, about 50% hair reduction with alexandrite and diode lasers 6 months after treatment, little evidence for IPL, Nd:YAG and ruby; the publisher answers 403 to curl, abstract verified through the NLM record PMID 17054211
• UK Health Security Agency: Laser radiation, safety advice · laser classes, Class 1C for cosmetic skin applications such as hair removal, Class 4 above 500 mW, Class 3B and 4 not suitable for consumers

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This guide is for general information. It does not replace medical or professional cosmetic advice or an examination.