Alexandrite Laser

In short: The alexandrite laser uses a chrysoberyl (alexandrite) crystal to produce light at 755 nm. Melanin absorbs this wavelength strongly, so long-pulsed alexandrite is used mainly for long-term hair reduction in light to medium skin, while short-pulsed (Q-switched or picosecond) alexandrite is used for some pigmented lesions and tattoos. In dark or tanned skin the risk of burns, dark marks and light patches rises, so suitability is decided at a physician consultation.

Definition

The alexandrite laser is a solid-state laser in which a chromium-doped chrysoberyl crystal emits near-infrared light at 755 nm. At this wavelength the main target (chromophore) is melanin. Melanin absorbs 755 nm more strongly than diode (800–810 nm) or Nd:YAG (1064 nm) wavelengths. In light skin this gives a strong effect on the hair follicle; in dark skin, epidermal melanin absorbs energy too, which narrows the safety margin.

“Alexandrite” does not describe a single type of device. There are two main groups, defined by pulse duration:

• Long-pulsed alexandrite: millisecond-domain pulses heat the hair follicle (selective photothermolysis). Its main use is hair reduction; some devices are also used for superficial pigmented lesions.
• Q-switched or picosecond alexandrite: very short pulses shatter pigment particles. They are used for solar lentigines, some dermal pigmented lesions and tattoo ink.

These are different devices with different indications under the same name. Which model is being used, and for what, needs separate verification.

How It Is Performed

For hair reduction the area is shaved and cleaned, and patient and operator wear eyewear rated for 755 nm. Alexandrite systems are usually combined with cold air, cryogen spray or contact cooling. When pigmented lesions are treated, the operator watches for a clinical endpoint on the lesion, such as brief whitening or darkening. 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.

Indications and Level of Evidence

• Long-term hair reduction: the Cochrane review reported short-term reduction of about 50% up to six months after the last session with alexandrite and diode lasers, and noted that the trials were of low methodological quality (Haedersdal and Gøtzsche, 2006). In randomised trials with follow-up of at least one hair cycle, average long-term reduction with alexandrite ranged from 35% to 84.25%, most appropriate on the legs and lowest on the face (Krasniqi et al., 2022).
• Compared with diode laser: in a side-by-side study of 15 untanned people, alexandrite and diode produced similar reductions 12 months after four sessions (Eremia et al., 2001). The sample was small and the result cannot be generalised.
• Hirsutism in PCOS: a systematic review found improvements in hirsutism severity and psychological outcomes with alexandrite laser, and greater effectiveness than IPL; the certainty of evidence was limited (Tan et al., 2024).
• Solar lentigines: in a randomised, evaluator-blinded study in Asian patients, a single session of picosecond 755 nm alexandrite, at the settings used, produced more lightening at 12 weeks than a 532 nm picosecond laser, with similar side effects (Vachiramon et al., 2022).

Skin Type (Fitzpatrick) Suitability and Risks

Alexandrite is generally used comfortably in Fitzpatrick I–III skin; from type IV upwards the decision needs more care. In a meta-analysis of studies in Fitzpatrick III–VI skin, alexandrite reduced hair counts more than IPL, with a similar safety profile and higher pain scores (Dorgham and Dorgham, 2020). A prospective series of 150 patients with Fitzpatrick IV–VI skin reported complications in 2% (Garcia et al., 2000); this single-centre observational result cannot be assumed for every device or operator.

As epidermal melanin increases, the energy the skin tolerates falls. In a study using melanin measurements, at the same melanin level the epidermis tolerated markedly more energy from Nd:YAG than from alexandrite (Lloyd et al., 2018). This is the physiological reason Nd:YAG is often preferred in dark skin.

• Expected, temporary effects: redness and swelling around follicles; with pigment treatment, darkening and crusting of the lesion.
• Burns, blisters and scarring: more likely with tanned skin, darker phototypes or unsuitable settings.
• Hyperpigmentation and hypopigmentation: seen particularly in darker skin; how long they last cannot be predicted.
• Paradoxical hypertrichosis: about 3% overall with laser and light hair removal, mostly on the face and neck, with no demonstrated link to device type (Snast et al., 2021).
• Eye injury: 755 nm light is strongly absorbed by the retinal pigment epithelium. Among direct eye injuries linked to dermatologic lasers, facial laser hair removal was the most common procedure, and most cases involved inadequate protection (Flegel et al., 2022). The brow and eyelid area is high risk.

Device and Model Verification

General claims such as “FDA-approved” or “CE-marked” are not enough; a link to a regulator’s homepage does not show that a specific model is authorised for a specific indication. This matters especially with alexandrite, because a long-pulsed hair removal system and a picosecond pigment system are different products. Ask for the exact brand and model, the pulse type (long-pulsed, Q-switched or picosecond), registration in Türkiye’s TİTCK Product Tracking System (ÜTS), the intended use covered by the CE marking, and which model and indication any FDA 510(k) clearance covers. Check these 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, hair colour and thickness, hormonal history, keloid tendency, vitiligo, herpes history, moles and pregnancy. Before a pigmented lesion is treated, it must be confirmed clinically as benign (with dermoscopy or biopsy if needed); a lesion without a clear diagnosis is not lasered. 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.

Timing after isotretinoin is the physician’s decision. A 2017 expert consensus found insufficient evidence to support delaying laser hair removal during or immediately after isotretinoin (Spring et al., 2017).

In darker phototypes or when the response is uncertain, the physician may choose a laser test spot. However, in the Fitzpatrick IV–VI series, pre-treatment testing was not related to whether complications developed (Garcia et al., 2000): a test spot gives useful information but is not a safety guarantee.

Realistic Expectations and Number of Sessions

For hair, the goal is long-term reduction; remaining hairs are usually finer. In one comparative study the number of sessions needed for the most appropriate result ranged from 3 to 7 (Toosi et al., 2006). In a retrospective study of relatively dark-skinned patients, hair reduction increased with the number of sessions, but side effects were also more frequent in the group with the most sessions (Bouzari et al., 2005). For pigmented lesions, the number of sessions depends on lesion type and depth, and some lesions recur. Sun protection is part of keeping the result.

When It Is Not Appropriate

• Freshly tanned or sunburnt skin
• Active infection, open wounds or active herpes in the area
• White, grey, red or very light hair (low response for hair reduction)
• An undiagnosed, changing or suspicious pigmented lesion
• Persisting with alexandrite in dark skin when a more suitable wavelength is available
• Pregnancy (elective procedures are usually postponed)
• Treatment inside the orbital rim without suitable internal eye protection

Comparison

The key differences between alexandrite, diode, Nd:YAG and IPL are wavelength, melanin absorption and skin-type fit. The difference between long-pulsed and picosecond alexandrite is pulse duration and purpose. The table on this page summarises them.

Alternatives and Combination Treatments

For hair reduction, Nd:YAG suits dark skin, diode lasers suit medium tones, and electrolysis is an option for light hair. For solar lentigines, 532 nm lasers, IPL or topical treatments are alternatives; for hormonal or inflammatory pigment problems such as melasma, topical treatment and sun protection come before any laser.

Our Clinical Approach

We base alexandrite decisions on skin type, hair or lesion characteristics and expectations. We tell the patient the brand, model and pulse type of the device, discuss the number of sessions as a range and explain possible side effects beforehand. Where a more suitable wavelength exists for darker skin, we recommend it.

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