The alexandrite laser emits light at 755 nm, a wavelength in the near-infrared spectrum that is strongly absorbed by melanin. That high melanin absorption makes it one of the most effective devices available for hair removal on light-to-medium skin, and a workhorse for treating benign pigmented lesions. The same property also makes it the wrong first choice for most patients with Fitzpatrick IV–VI skin, where the melanin in the epidermis competes with the target and raises the risk of burns and post-inflammatory hyperpigmentation (PIH).
This guide covers what the alexandrite laser treats, how it compares to other common wavelengths, who is and is not a candidate, and what to expect before, during, and after treatment.
How the alexandrite laser works
All aesthetic lasers operate on the principle of selective photothermolysis: a specific wavelength of light is absorbed by a target chromophore (melanin, hemoglobin, or water), converted to heat, and the heat damages the target while sparing surrounding tissue.
The alexandrite laser uses a chromium-doped beryllium aluminate (alexandrite) crystal as its lasing medium. The 755 nm wavelength it produces sits in a sweet spot for melanin absorption — higher than the longer 810 nm diode or 1064 nm Nd:YAG wavelengths, but lower than the 694 nm ruby laser. In practical terms, this means the alexandrite:
- Absorbs strongly in melanin, making it highly effective for targets rich in pigment (hair follicles, pigmented lesions, tattoo ink).
- Penetrates to a moderate depth in the dermis — deep enough to reach most hair follicles, but shallower than the Nd:YAG.
- Has a relatively wide safety margin on light skin (Fitzpatrick I–III) because there is little competing melanin in the epidermis.
The laser can operate in long-pulse mode (for hair removal and vascular lesions) or Q-switched mode (for pigmented lesions and tattoo removal). The pulse duration determines the primary target and the tissue effect.
FDA-cleared uses
The FDA has cleared multiple alexandrite laser platforms — including the Cynosure Apogee, Candela GentleLase, and Cutera Excel V — for several indications:
- Hair removal (long-pulse mode). Permanent hair reduction on body and facial areas.
- Benign pigmented lesions (Q-switched or long-pulse). Solar lentigines, freckles, café-au-lait macules, and other epidermal pigmentation.
- Vascular lesions. Some platforms are cleared for telangiectasia and spider veins.
- Tattoo removal (Q-switched mode). Particularly effective for blue, green, and black tattoo ink.
Off-label uses commonly performed by dermatologists include treatment of hidradenitis suppurativa scarring, folliculitis decalvans, and onychomycosis, but these applications have a smaller evidence base.
Alexandrite laser for hair removal
Hair removal is the most common use of the alexandrite laser. The 755 nm wavelength targets melanin in the hair shaft and matrix, heating the follicle enough to disable it during the anagen (growth) phase.
Efficacy
Clinical data consistently shows 70–80% long-term hair reduction after a full course of 4–8 treatments spaced 4–6 weeks apart. A prospective study reported mean hair reduction of approximately 74% across Fitzpatrick skin types I–III after six treatments, with results persisting at 18-month follow-up. Individual response depends on hair color, hair thickness, hormonal status, treatment area, and adherence to the session schedule. The AAD notes that patients can expect approximately 10–25% reduction after the first treatment, with cumulative improvement building over subsequent sessions.
Fine or light-colored hair (blonde, red, gray, white) responds poorly because it contains less melanin to absorb the laser energy. A retrospective study found that fair hair showed only about 10% clearance with alexandrite treatment.
Treatment parameters by skin type
| Skin type | Typical fluence | Pulse duration | Expected reduction |
|---|---|---|---|
| Fitzpatrick I | 35–50 J/cm² | 10 ms | ~78% |
| Fitzpatrick II | 30–40 J/cm² | 10 ms | ~74% |
| Fitzpatrick III | 25–35 J/cm² | 10–20 ms | ~70% |
| Fitzpatrick IV | 20–30 J/cm² | 20 ms (with cooling) | Variable, higher PIH risk |
These are general ranges. The treating provider adjusts fluence, pulse duration, spot size, and cooling based on individual assessment and patch-test response.
What a session involves
- Preparation. Shave the treatment area 24 hours before the appointment. Avoid waxing, tweezing, or bleaching for 4 weeks prior, because the root must be present for the laser to target. Avoid sun exposure and tanning for at least 2 weeks.
- Treatment. The provider applies a cooling gel or uses the device's integrated cooling (such as cryogen spray) to protect the epidermis. The laser handpiece is passed over the skin, delivering pulses that feel like a rubber band snapping or a warm pinprick.
- Afterward. Redness and mild swelling are normal for a few hours. Pigmented hair stubble may shed over 1–3 weeks as the follicle expels the damaged hair. Avoid sun exposure, hot showers, and strenuous exercise for 24–48 hours.
Alexandrite for pigmented lesions and tattoo removal
In Q-switched mode, the alexandrite laser delivers nanosecond pulses that shatter pigment particles without significant heat diffusion to surrounding tissue. This makes it effective for:
- Solar lentigines and freckles. Often clears in 1–3 sessions.
- Café-au-lait macules. Variable response; recurrence is common and may require maintenance treatments.
- Blue and green tattoo ink. The 755 nm wavelength is absorbed well by blue and green pigments. Black ink also responds, though the Nd:YAG (1064 nm) is often preferred for black because it penetrates deeper.
- Nevus of Ota and dermal melasma. Q-switched alexandrite has been used for these conditions, but the evidence is mixed, and the risk of PIH in darker skin types limits its use to lighter skin.
Skin of color: why the alexandrite is not the default
This is where the 755 nm wavelength's strength becomes a liability. In Fitzpatrick IV–VI skin, the epidermis contains more melanin. The alexandrite laser cannot distinguish between the melanin in a hair follicle or pigmented lesion and the melanin in the surrounding skin. The result: the epidermis absorbs energy alongside the target, which can cause burns, blistering, hyperpigmentation, or hypopigmentation.
A 2025 meta-analysis of laser hair removal in Asian skin (Fitzpatrick III–V) found that the alexandrite laser posed a higher risk of hyperpigmentation compared to the diode and Nd:YAG, and that the Nd:YAG had the safest profile for darker skin types, though it may require more sessions for equivalent results.
For Fitzpatrick IV–VI skin, the recommended alternatives are:
- Nd:YAG (1064 nm). Longer wavelength penetrates deeper and is less absorbed by epidermal melanin. Safer for darker skin, though slightly less efficient per session.
- Diode (810 nm). A middle ground between alexandrite and Nd:YAG; effective for Fitzpatrick II–V with appropriate settings.
Many modern platforms offer dual-wavelength capability (e.g., Candela GentleMax Pro combines 755 nm alexandrite and 1064 nm Nd:YAG), allowing the provider to switch between wavelengths based on skin type and treatment area in the same session.
Alexandrite vs. other hair-removal wavelengths
| Feature | Alexandrite (755 nm) | Diode (810 nm) | Nd:YAG (1064 nm) | IPL (500–1200 nm) |
|---|---|---|---|---|
| Best skin types | I–III | II–V | III–VI (safest for V–VI) | I–III |
| Melanin absorption | High | Moderate | Low | Variable (broad spectrum) |
| Hair color response | Dark hair only | Dark to medium | Dark hair | Dark hair only |
| Sessions needed | 4–8 | 6–10 | 6–12 | 6–12 |
| Speed | Fast (large spot sizes) | Moderate | Moderate | Fast |
| PIH risk in dark skin | High | Low–moderate | Low | Moderate–high |
| Precision | High (single wavelength) | High | High | Lower (broad spectrum) |
Side effects and risks
Common (typically transient):
- Redness and swelling at the treatment site (resolves in hours to days).
- Mild discomfort during treatment (described as snapping or stinging).
- Temporary darkening of pigmented spots before they flake off (normal for pigment treatments).
Less common:
- Blistering or crusting, particularly if fluence is too high or the skin is tanned.
- Transient hyperpigmentation or hypopigmentation, especially in Fitzpatrick III–IV skin.
- Paradoxical hypertrichosis (increased hair growth), a rare reaction more commonly seen in Fitzpatrick III–VI patients treated on the face.
Rare but serious:
- Scarring (uncommon with proper technique and settings).
- Ocular injury if protective eyewear is not used correctly.
The AAD recommends that laser treatments be performed by a board-certified dermatologist or a provider under direct dermatologist supervision, because improper device selection and settings account for the majority of preventable complications.
Contraindications
The alexandrite laser should be avoided or used with extreme caution in patients who:
- Have Fitzpatrick IV–VI skin (consider Nd:YAG or diode instead).
- Are actively tanned or have had recent sun exposure.
- Have a history of keloid scarring.
- Are taking photosensitizing medications (isotretinoin within the past 6 months, certain antibiotics, St. John's wort).
- Are pregnant or breastfeeding (lack of safety data; precautionary avoidance).
- Have active skin infections, open wounds, or inflammatory skin conditions in the treatment area.
- Have a personal or family history of melanoma in the treatment area.
Questions to ask your provider
Before booking an alexandrite laser treatment, ask:
- "What is your experience with this device on my skin type?" The provider should be able to tell you how often they treat patients with your Fitzpatrick type and what their complication rate is.
- "Will you do a patch test first?" A test spot on a small area, observed for 24–48 hours, helps confirm that the settings are safe for your skin before treating a larger area.
- "What wavelength are you using, and is it the safest option for my skin?" If you have olive or darker skin and the provider plans to use 755 nm, ask why they are not using 1064 nm Nd:YAG.
- "How many sessions do I need, and what results can I realistically expect?" The provider should give you a treatment plan with an estimated session count and expected outcome.
- "What is your protocol if something goes wrong?" Any provider performing laser treatments should have a plan for managing burns, PIH, or unexpected reactions.
Sources
- DermNet. "Alexandrite Laser Treatment Explained." DermNet New Zealand, 2026. https://dermnetnz.org/topics/alexandrite-laser-treatment
- American Academy of Dermatology. "Laser Hair Removal: FAQs." AAD, 2026. https://www.aad.org/public/cosmetic/hair-removal/laser-hair-removal-faqs
- StatPearls. "Laser Hair Removal." National Library of Medicine, NCBI Bookshelf, 2026. https://www.ncbi.nlm.nih.gov/books/NBK507861
- Pun J, Zancanaro P, et al. "Assessing the Safety of the Q-Switched 755-nm Alexandrite Laser in Darker Skin: A Retrospective Study." Journal of the American Academy of Dermatology, 2022;86:909–911. https://pubmed.ncbi.nlm.nih.gov
- J Cosmet Med. "Laser Hair Removal for Fitzpatrick Skin Types III–V: Efficacy and Safety in Asian Skin — A Meta-Analysis of 10 RCTs." Journal of Cosmetic Medicine, 2025. https://www.jcosmetmed.org/journal/view.html?doi=10.25056%2FJCM.2025.9.1.1
- U.S. Food and Drug Administration. "Aesthetic/Cosmetic Devices." FDA, 2026. https://www.fda.gov/medical-devices/products-and-medical-procedures/aesthetic-cosmetic-devices
- Cleveland Clinic. "Laser Hair Removal: How It Works & What to Expect." Cleveland Clinic, 2026. https://my.clevelandclinic.org/health/treatments/21757-laser-hair-removal
