Diode Laser

In short: A diode laser is a semiconductor laser that most often emits light around 800–810 nm. It targets melanin in the hair follicle, and its main use is long-term hair reduction. Randomised trials show a meaningful reduction in hair counts, but results vary between people and complete, lasting hair loss cannot be promised. Because darker or tanned skin carries a higher risk of burns and pigment change, the device, settings and patient selection are decided by the physician.

Definition

A diode laser produces light from arrays of semiconductor diodes. The diode lasers most used in aesthetic medicine emit in the near-infrared, usually at 800–810 nm; 755 nm and 940 nm diode modules exist too, as do platforms that combine several wavelengths in one handpiece. “Diode laser” is therefore a family of technologies rather than a single device.

It works by selective photothermolysis. Melanin in the hair shaft and bulb absorbs light at this wavelength and turns it into heat. The heat spreads to the structures that make hair, including the stem-cell-rich bulge, and reduces their capacity to regrow hair. Melanin absorbs diode wavelengths less strongly than the 755 nm alexandrite wavelength, but the light penetrates deeper. For medium skin tones this gives a little more margin to protect the epidermis. The 1064 nm Nd:YAG laser usually offers a wider safety margin in dark skin.

Because the method depends on melanin, white, grey, red and very fair blond hairs usually respond poorly. Only a share of follicles is in a responsive growth phase at any one session, which is the main reason several sessions are needed.

How It Is Performed

The area is shaved and cleaned, and both patient and operator wear eyewear rated for the device’s wavelength. Diode handpieces usually have contact sapphire cooling or a similar system, so heat is directed to the follicle while the skin surface is protected. Some devices fire single pulses; others use a low-energy, high-repetition technique in which the handpiece keeps moving over the area, an approach assessed in small randomised studies (Barolet, 2012).

Energy density, pulse duration, spot size and cooling are not values for patients to choose; the physician sets them for the specific device (following the manufacturer’s instructions), the skin type and the treatment area. Patients feel heat and a snapping sensation; how strong it feels depends on the area, hair density and individual sensitivity.

Indications and Level of Evidence

• Reducing unwanted hair: the main indication. A Cochrane systematic review (Haedersdal and Gøtzsche, 2006) reported short-term hair reduction of about 50% up to six months after the last session with alexandrite and diode lasers. The same review stressed that the included trials were of low methodological quality and that long-term hair removal had not been documented at that time.
• Long-term results: a review of five randomised trials with follow-up of at least one full hair cycle found average long-term reductions of 32.5% to 69.2% for diode lasers, with better results on the legs than on the face (Krasniqi et al., 2022).
• Comparison between devices: a network meta-analysis of 13 randomised trials found significantly lower hair counts with diode laser than with control at three and six months, and no significant difference between laser types (Kao et al., 2023).
• Hirsutism in PCOS: in a systematic review, diode laser combined with metformin or a combined oral contraceptive worked better than diode laser alone; the certainty of evidence was low (Tan et al., 2024). The hormonal cause of hirsutism needs its own assessment.

Much of the evidence comes from small studies using different protocols. Percentages reported for one brand cannot be transferred directly to another device or to an individual patient.

Skin Type (Fitzpatrick) Suitability and Risks

The Fitzpatrick I–VI scale roughly describes how skin reacts to sun and how much epidermal melanin it has. Epidermal melanin competes with follicular melanin: in dark or tanned skin, part of the energy is absorbed at the surface. In a meta-analysis of studies in Fitzpatrick III–VI skin, diode laser did not differ significantly from IPL in hair reduction and had a similar safety profile, with higher pain scores (Dorgham and Dorgham, 2020). A recent review recommends conservative settings, strict sun protection and a step-by-step approach in skin of colour, and notes the lack of large prospective trials in this group (Dreifus et al., 2026).

• Expected, temporary effects: redness and swelling around the follicles usually settle within hours to days.
• Burns and blisters: more likely in tanned skin, darker phototypes or with unsuitable settings; crusting and scarring are possible.
• Post-inflammatory hyperpigmentation (PIH) and hypopigmentation: more common in darker skin; they often fade over months, but the time course cannot be predicted.
• Paradoxical hypertrichosis: increased hair growth in or near the treated area. A meta-analysis found an overall rate of about 3%, mostly on the face and neck (Snast et al., 2021).
• Moles: lightening, shrinkage and changes in dermoscopic pattern have been reported in melanocytic naevi treated during laser hair removal. Because these changes can confuse later monitoring, suspicious moles should be assessed beforehand and shielded from the laser (Cices et al., 2023).
• Eye safety: a review of 60 direct eye injuries linked to dermatologic lasers found that facial laser hair removal was the most common procedure and that appropriate eye protection was not used in 73% of cases (Flegel et al., 2022). The brows and eyelids are high-risk areas; treatment inside the orbital rim is considered only with suitable internal eye shields and on the physician’s decision.

Device and Model Verification

General claims such as “FDA-approved” or “CE-marked” are not enough on their own. A link to a regulator’s homepage, or general information about a device class, does not show that a particular model is authorised for a particular indication. Useful questions for patients are: What is the exact brand and model? At what wavelength does it work? Is it registered in Türkiye’s TİTCK Product Tracking System (ÜTS)? Which intended use does its CE marking cover in Europe, and for which model and indication was any US FDA 510(k) clearance granted? These details should be checked against the device label, the instructions for use and official databases.

Pre-Procedure Assessment and Test Spots

The consultation covers skin type, recent sun exposure and tanning, hair colour and thickness, hormonal history, any tendency to keloids or abnormal scarring, vitiligo, active infection or a history of herpes, the state of any moles, and pregnancy. Tell your physician about all medicines and supplements, including photosensitising medicines and blood thinners. Never stop a prescribed medicine without asking the doctor who prescribed it.

For people taking isotretinoin, or who have recently finished it, timing is the physician’s decision. A 2017 systematic review with expert consensus found insufficient evidence to support delaying laser hair removal during or immediately after isotretinoin (Spring et al., 2017); the decision weighs the individual’s skin against current evidence.

With darker phototypes, a new device or an uncertain skin response, the physician may choose a laser test spot on a small area. It gives information about early reactions, but it does not guarantee how the whole treatment area will respond.

Realistic Expectations and Number of Sessions

The accurate description is long-term hair reduction, not eradication. Remaining hairs are often finer and lighter. In one comparative study the number of sessions needed to reach the most appropriate result ranged from 3 to 7 (Toosi et al., 2006). Intervals follow the hair cycle of the area. Hormonal status, body area, hair colour and the device strongly affect the result, and some people need maintenance sessions over time. Sun protection and avoiding irritation in the days after treatment matter.

When It Is Not Appropriate

• Active infection, open wounds or an active herpes lesion in the area
• Freshly tanned or sunburnt skin
• White, grey or very light hair (low chance of response)
• Moles that have not been assessed, are changing or look suspicious
• Pregnancy (elective procedures are usually postponed because safety data are limited)
• The eyelids and the area inside the orbital rim without suitable internal eye protection
• Unrealistic expectations, or being unable to protect the skin from sun after treatment

Comparison

Diode, alexandrite, Nd:YAG and IPL can all be used for hair reduction, but they differ in wavelength, melanin absorption and skin-type fit. There is no single “most appropriate” device; the choice depends on skin type, hair characteristics and body area. The table on this page summarises the differences.

Alternatives and Combination Treatments

For light-coloured hair, electrolysis, IPL or temporary methods such as shaving and waxing are options. In hirsutism, laser treatment can be planned alongside hormonal assessment and, where needed, medical treatment (Tan et al., 2024).

Our Clinical Approach

At our clinic, a diode laser decision starts with an examination of skin type, hair characteristics, moles and medication history, and the brand and model of the device are shared with the patient. We describe the goal as long-term reduction, give the number of sessions as a range rather than a fixed figure, and explain possible side effects before treatment.

Sources and References

This article is based on PubMed-indexed systematic reviews, meta-analyses, randomised trials and safety reviews. It is not a personal diagnosis or treatment instruction.

Last medical review: 23 September 2026 · Medical editor: Dr. Hamza Gemici