Laser hair removal: how it works, sessions and risks

How does the laser work?

The principle is called selective photothermolysis: the light is absorbed mainly where there is a lot of pigment – in dark hair and in the hair root – while the surrounding skin stays comparatively cool. If the heat keeps the follicle at the required temperature for long enough, the follicle loses its ability to grow new hair. That is why contrast matters: the darker the hair and the lighter the skin, the more precisely the laser works.

Different wavelengths penetrate to different depths. 755 nm is strongly absorbed by melanin and acts close to the surface, 810 nm lies in the middle, and 1064 nm penetrates deepest and is absorbed least by the melanin of the epidermis – which is why it is the safer choice for darker skin types. Modern diode lasers emit several of these wavelengths at the same time.

Why does it take several sessions?

Every hair goes through a cycle of growth (anagen phase), transition (catagen phase) and rest (telogen phase). The laser only acts on hairs in the growth phase, because only then are the hair and the hair root connected, so the heat reaches the root. At any given time, that is only some of the hairs in an area.

So the treatment is repeated at intervals of 4 to 6 weeks until as many follicles as possible have been reached at the right moment. As a rule it takes 6 to 10 sessions; exactly how many depends on the body area, hair thickness, skin type and hormonal factors.

What do studies show?

Two randomised comparative studies have compared the gliding diode laser technique (many passes at low energy) with the classic single-pulse technique. In the study by Braun (2011) with 22 patients, both techniques produced a comparable hair reduction of 90 to 94 per cent after five sessions – measured 6 and 18 months after the last treatment. The gliding technique was considerably less painful.

Koo and colleagues (2014) compared two 810 nm diode lasers on the legs and underarms: six months after five sessions, the number of hairs had fallen by 40.7 per cent (gliding technique) and 33.5 per cent (single pulse) respectively – a difference that was not statistically significant. Participants rated the pain at 2.7 versus 3.6 on a scale up to 10, and the results were still holding at 12 months. These figures are study results, not a promise for an individual treatment.

Laser, IPL or waxing?

¹ Permanent hair reduction requires several treatments, depending on the body area and the individual hair and skin type. Success cannot be guaranteed, even when the treatment is carried out professionally. On light, red, grey or white hair, the treatment is ineffective or only partially effective.

Who is allowed to use lasers in Germany?

The use of lasers and IPL devices for cosmetic purposes is governed by the Ordinance on Protection against the Harmful Effects of Non-Ionising Radiation in Applications on Humans (NiSV). Since 31 December 2022, hair removal with laser or IPL may only be carried out by someone who can prove certified expertise under Annex 3 of the NiSV. Removing tattoos and treating pigmented moles with a laser is reserved for doctors.

Ask the studio for proof of this expertise (Fachkunde-Nachweis) – a reputable provider will show it to you without hesitation.

Side effects and risks

Redness and slight swelling are common and temporary; they settle within a few hours to two days. Blisters, crusts or temporary changes in pigmentation are rare. Very rarely – and almost only on the face and neck – more hair grows after the treatment instead of less (paradoxical hypertrichosis).

When the laser is not used

• use of photosensitising medication (e.g. certain antibiotics, isotretinoin, St John's wort)
• light-induced dermatoses and cutaneous porphyrias
• acute skin conditions, sunburn or a fresh tan in the treatment area
• pregnancy and breastfeeding

Moles and tattoos are avoided. Please have any unusual pigmented moles checked by a dermatologist beforehand.

Sources

1. Bundesamt für Strahlenschutz: Laser, IPL & Co – Anwendungen optischer Strahlung in der Kosmetik. UMID – Umwelt und Mensch Informationsdienst 1/2016. [German Federal Office for Radiation Protection: applications of optical radiation in cosmetics] umweltbundesamt.de/sites/default/files/medien/2218/publikationen/umid_1_2016_bfs_laser.pdf
2. Verordnung zum Schutz vor schädlichen Wirkungen nichtionisierender Strahlung bei der Anwendung am Menschen (NiSV) [Ordinance on Protection against the Harmful Effects of Non-Ionising Radiation in Applications on Humans], in particular § 5 and Annex 3 (certified expertise). gesetze-im-internet.de/nisv
3. Braun M. Comparison of high-fluence, single-pass diode laser to low-fluence, multiple-pass diode laser for laser hair reduction with 18 months of follow up. J Drugs Dermatol. 2011;10(1):62–65. pubmed.ncbi.nlm.nih.gov/21197525
4. Koo B, Ball K, Tremaine AM, Zachary CB. A comparison of two 810 diode lasers for hair removal: low fluence, multiple pass versus a high fluence, single pass technique. Lasers Surg Med. 2014;46(4):270–274. pubmed.ncbi.nlm.nih.gov/24752608

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Laser hair removal at MOOD Beauty in Munich

We treat with the Alma Soprano ICE Platinum diode laser in our studio at Theresienstraße 38 in Munich-Maxvorstadt. Every treatment begins with a free initial consultation including a test patch.