The short answer
Laser hair removal can leave you with fewer hairs for months or years. Some hair can regrow, and keeping an area hair-free may require maintenance treatments. That is the expectation described by the American Academy of Dermatology.
The studies below counted hairs months after treatment, compared counting methods and asked patients whether they still needed hair removal.
What does “permanent hair reduction” mean?
In an FDA clearance document for the Hera and Armo laser systems, permanent hair reduction means a stable decrease in the number of regrowing hairs at specified follow-up dates.
Why are several sessions needed?
Laser treatment uses heat absorbed by pigment in the hair to damage the follicle. Hair follicles pass through different growth stages, and the active growth stage is the target for treatment. Because follicles are not all in that stage at once, a single appointment cannot treat every hair equally. Cleveland Clinic explains the growth cycle.
The two randomized trials below used four sessions. A provider may recommend a different course for your treatment area, hair, skin and device. The AAD describes regrowing hair as often finer and less noticeable, and says maintenance treatments may be needed to keep an area clear. AAD guidance on results and maintenance.
What does the wider evidence show?
The trials reported mean long-term hair reductions of about 30–74% for Nd:YAG, 35–84% for alexandrite and 33–69% for diode lasers. Leg-hair trials reported greater reductions than facial-hair trials. These ranges come from different treatment settings, body areas and study protocols, so they cannot rank the devices or predict your result. The reviewers could not pool the data into a meta-analysis and called for larger, standardized trials. Krasniqi et al., 2022
A 2023 network meta-analysis included 13 randomized trials and 652 participants, with comparisons at up to three months and around six months. Diode laser reduced hair counts compared with control, while the analysis found no statistically significant difference between laser interventions. The two reviews examined different follow-up windows, so their trial counts are not directly comparable. Neither review establishes lifetime clearance.
How long did researchers follow the results?
The 2008 trial followed leg hair for 18 months and counted it two ways. The 2026 trial compared professional IPL with diode laser on underarms and checked results about seven months after treatment.
| Study | Treatment and participants | Follow-up after the last session | Participants at the final check |
|---|---|---|---|
| Davoudi et al., 2008 | Four sessions using alexandrite, Nd:YAG or both on small areas of black leg hair; skin types III–IV | 18 months | 15 of 20 enrolled |
| Barros et al., 2026 | Four planned sessions; women received professional IPL in one underarm and diode laser in the other; skin types I–IV | 30 weeks, approximately seven months | 20 of 48 who started treatment |
The authors suggested photographs may have missed thin residual hairs. They also noted that the comparative reliability of the two counting methods had not been established. Davoudi et al., measurement limitations
In the 2026 trial, the authors’ statistical model found no significant difference in hair counts at the primary assessment, four weeks after treatment. Diode laser produced lower counts at the 30-week follow-up. The percentages below describe the participants who attended that later visit. Barros et al., results
Recruitment stopped at 48 of the planned 62 participants. Missing visits leave uncertainty about the others’ outcomes. HTM Eletrônica supplied the IPL device; the authors reported no sponsor influence on the study. Study limitations and support.
Can some hair remain without needing removal?
An alexandrite laser follow-up study asked 100 selected patients about their hair reduction and satisfaction. All said they no longer needed epilation because the remaining hairs were too thin to notice. The authors describe a period of at least two years after treatment. Altunel and Kartal, study abstract.
The researchers selected these 100 from 183 patients because they had stopped epilation. That selection prevents us from calculating another patient’s chance of the same outcome. The results also came from questionnaires, so they reflect patients’ perceptions of their hair and need for removal.
When discussing a course with a provider, say what you want to change: fewer hairs, finer regrowth, less frequent shaving or skin that stays completely clear. Each goal calls for a different way of judging the result.
Does facial hair follow the same pattern?
The AAD’s overview identifies hormonal influences as a reason results on a woman’s face may be less permanent than on other body areas.
A 2024 systematic review in JAMA Dermatology examined six studies involving 423 women with polycystic ovary syndrome (PCOS) and hirsutism, or excess hair growth. Laser and light treatments improved hair-growth severity and related psychological outcomes. Some studies reported additional benefits when treatment was combined with medication.
The reviewers judged the evidence to be of low certainty and could not pool the results. These findings support discussing the hormonal context with a clinician; they cannot tell an individual patient how long their result will last.
Laser and IPL can also cause paradoxical hypertrichosis, an increase in hair growth after treatment. A 2021 systematic review found this complication was associated with treatment on the face or neck and was rare elsewhere. For facial treatment, ask the provider how they assess that risk for your hair and skin.
What should a treatment claim tell you?
A provider quoting a reduction percentage should be able to name the measurement, time after the final session, treated body area and participants. Ask whether the evidence covers people with hair and skin like yours. The AAD lists hair color and thickness, treatment area, laser type and skin color among factors that affect results. AAD guidance.
The two randomized trials above tested professional equipment. Their results cannot establish the performance of a home device.
The AAD lists redness, swelling and discomfort among common side effects, and blistering, scarring and pigment changes among other possible complications. Some pigment changes can be permanent. AAD safety information.
Before paying for a course, ask the provider: “With this device, on this body area, what reduction is realistic a year after my final session, what risks apply to my skin, and might I need maintenance treatments?”
Sources and how we checked them
Prepared by BeautyPlaces using a focused selection of reviews, trials and patient guidance. The 2008 trial provides 18-month follow-up and two counting methods; the 2026 trial provides a recent underarm comparison. We checked both full texts. The source list records which texts were available for checking.
- American Academy of Dermatology: FAQs and overviewPatient guidance checked: expectations, maintenance, facial hair and risks.
- FDA K212793: Hera and Armo clearance summaryDevice-specific wording for permanent hair reduction.
- Cleveland Clinic: laser hair removalHow treatment relates to the hair growth cycle.
- Krasniqi et al., 2022: systematic reviewAbstract and accessible article sections checked: long-term reductions, follow-up criteria and variation between trials.
- Kao et al., 2023: network meta-analysisAbstract checked: 13 randomized trials and comparisons at up to three and around six months.
- Davoudi et al., 2008: randomized leg-hair trialFull text checked: 18-month results and two hair-counting methods.
- Barros et al., 2026: randomized IPL and diode trialFull text checked: underarm results, participant flow and device support.
- Altunel and Kartal: long-term alexandrite follow-upAbstract checked: questionnaires from selected patients who had stopped epilation. Published online in 2021 in a journal issue dated 2020.
- Tan et al., 2024: systematic review of laser and light therapies in PCOSAbstract checked: hirsutism outcomes and low certainty of the evidence.
- Snast et al., 2021: systematic review of paradoxical hypertrichosisAbstract checked: increased hair growth after laser or IPL, particularly on the face and neck.
Sources checked on .