Efficacy and safety of intense pulsed light therapy (IPL 690nm) and triple wavelength diode laser (755nm, 810nm, 1064nm) in treating lower face hirsutism in Fitzpatrick phototype III-V: A randomised split-face interventional study

Introduction

Hirsutism is defined as the presence of terminal coarse hair in females in an androgen-dependent, male pattern distribution, such as on the chin, upper lip, chest, breasts, abdomen, back, and anterior thighs.¹ About 5-10% of women of reproductive age suffer from hirsutism, which poses both cosmetic and psychological challenges.¹ It is usually caused by excess androgens linked to polycystic ovarian syndrome (PCOS), which is the most common etiology.² The second most common cause is idiopathic hirsutism.²

Laser hair reduction occurs by selective photothermolysis, where melanin in hair is the chromophore.³ Laser hair reduction is considered permanent when there is a sustained decrease in terminal hair growth beyond the complete growth cycle of a specific area.⁴ Complete permanent hair removal is not possible with lasers, but they do provide a significant delay in hair re-growth and replace coarse hair with finer vellus hair.⁴ Laser apparatus is very expensive, but IPL machine is far more affordable, and many dermatologists use IPL for hair reduction. However, there are only a few studies comparing the laser and light-based technologies for permanent hair reduction in dark skin types. Thus, we conducted this split-face trial comparing the two most common hair removal devices used in practice, i.e., an intense pulsed light (IPL) device and a triple-wavelength diode laser.

Methods

It was a randomised split-face interventional study conducted at a tertiary care hospital, comprising 33 female patients of lower face hirsutism diagnosed on detailed history and complete cutaneous and physical examination, between the ages of 18-45 years with Fitzpatrick phototype III-V. The exclusion criteria included prior laser hair removal, endocrine disorders, active or recurrent skin infections in the area to be treated, and tendency for scar or keloid formation. All participants signed a written informed consent. The study received prior approval from the ethics committee of the hospital.

Four sessions of treatment with a triple wavelength diode laser (755nm, 810nm, 1064nm, Alma Soprano Titanium diode laser machine with a spot size of 5x5 mm and sapphire tip cooling) were done on one side of the face, while IPL (690 nm filter, Sparsh E-light machine, spot size of 15x50 mm) was used on the other side. Both treatments were administered in four sessions, spaced 4-6 weeks apart [Table 1]. The 4-6-week interval between sessions was chosen to align with the anagen phase of the hair follicle, which is most responsive to laser treatment. Most participants showed sufficient regrowth at 4 weeks; in those with slower regrowth, sessions were scheduled at a 6-week interval. The choice of technology for each side was determined randomly using opaque envelopes. Only the performing clinician knew which technology was assigned to each side, and each device was consistently used on the same treated area throughout the study.

A razor was used to remove visible hair shafts before each session. Treatment parameters followed the manufacturers’ guidelines, starting with the minimum recommended fluence and increasing by 1 or 2 Joules/cm² in subsequent sessions, depending on the patient’s tolerance, clinical end-points (perifollicular erythema and oedema), and reported pain. The triple wavelength diode laser has a power ranging from 800-2400W, a pulse duration of 17 to 30 ms, and a frequency of 1 to 10 Hz, while the IPL has a power of 500 to 2000W, a pulse width of 8, 9, or 10 ms, and pulse delay of 10 ms [Table 1].

During each session, the skin was treated using one pass of horizontal stamps followed by another pass of vertical stamps with a maximal overlap of 10% using hair removal (HR) mode of the machine, and cooling was done before, between, and after the passes using an inbuilt sapphire tip contact cooling system.

Close-up clinical photographs were taken before and after treatments with a digital camera. Patients were evaluated before treatment and at each visit for the following parameters.

The number of hairs was calculated at baseline in an area of 2 cm² with the greatest hair density, before each session, and one month after the last session. A digital camera was used to take photographs of the predefined area. The photographs were analysed by a blinded evaluator, who counted the absolute number of hair shafts. The patient was also asked to report the time taken for hair regrowth after each session. Patient’s opinion with the results of treatment was recorded as fully satisfied, satisfied, or unsatisfied.

Side effects were recorded immediately after treatment, such as pain, burning, persistent erythema, and swelling. The patient was also asked about the long-term side effects from previous treatment, such as hypo- or hyperpigmentation, secondary infection, folliculitis, and paradoxical hypertrichosis.

Results

Our study included 33 patients aged 19-44 years. Of these, 39% (n=13) were aged between 26 to 35 years, 36% (n=12) between 19 to 25 years, and 24% (n=8) between 36 to 45 years.

After randomisation, 42.42% of participants were treated with a triple-wavelength diode laser, and 57.58% were treated with IPL on the left side of the face. Around 57.58% were treated with the triple wavelength diode laser, and 42.42% were treated with IPL on the right side. No significant difference was observed in the absolute hair count at the baseline between the triple wavelength diode laser (21.09 ± 7.22) and IPL (20.58 ± 6.73) groups (p-value = 0.431).

However, significant differences were noted in the absolute hair counts at subsequent sessions, with the triple wavelength diode group showing progressively lower counts compared to the IPL group across all sessions and after one month of the last sitting. The mean percentage of hair reduction was significantly higher in the triple wavelength diode group (74.15 ± 5.38%) compared to the IPL group (46.47 ± 6.91%) after one month of the 4^th sitting (paired t-test, p-value <0001). Patients in the triple wavelength diode group reported a mean hair regrowth time of 22.67 ± 1.78 days one month after the fourth session, compared to 13.58 ± 0.94 days in the IPL group (paired t-test, p < 0.0001). Visual analogue scale was also used to assess patient satisfaction, and the mean patient satisfaction score was significantly higher in the triple wavelength diode group (8.79 ± 1.52) compared to the IPL group (5.03 ± 1.16) (paired t-test, p-value <0001).

Both groups had a comparable proportion of side effects. Pain was reported in 33.33% of patients in the triple wavelength diode group and 57.58% in the IPL group. Transient erythema was observed in all patients, while other side effects such as burn, hyperpigmentation, folliculitis, scarring, secondary infection, and paradoxical hypertrichosis were variably reported, but not statistically significant between the two groups. Secondary infection was treated with oral and topical antibiotics, while patients with paradoxical hypertrichosis were treated with increased energy fluence in their subsequent sittings.

Discussion

Hair reduction using IPL and triple wavelength diode lasers is based on the extended theory of selective photothermolysis (ESP), a concept introduced by Parish and Anderson.^3,5 The primary chromophore in hair removal is melanin, and maximum heat is delivered to this chromophore, which is then transferred to the hair bulb where the stem cells reside, resulting in hair removal. In order for this heat dissipation to take place, the pulse duration should be higher than the thermal relaxation time of the chromophore.^3,5 Melanin, which consists of eumelanin and pheomelanin in varying proportions, absorbs light differently across wavelengths. Within the range of 700-1000 nm, melanin absorbs the most heat, while water and haemoglobin absorb much less.^3,5 However, ESP is more commonly associated with SHR (super hair removal) or in the motion mode of laser hair removal, which was not employed in our study.⁶ We chose to use the standard HR (hair removal) mode to ensure consistency with the IPL protocol and to allow a fair comparison.

The broad absorption spectrum of melanin allows for the use of various lasers, such as the ruby (694 nm), alexandrite (755 nm), diode (810 nm), and Nd: YAG (1064 nm), as well as IPL (500-1200 nm). Treatments outside the 700-1000 nm range may lead to unnecessary skin heating with limited benefits in hair removal. In this study, we employed a triple-wavelength diode laser with a wavelength of 755 nm, 810 nm, and 1064 nm, and an IPL with a filter bandwidth of 690-1200 nm.^4,6

Designing comparative studies in hair removal is challenging due to inherent differences in the devices, which vary in fluence, energy delivery methods, and shooting times. The treatment area, frequency, gap between treatments, and parameters need to be kept consistent.^4,6 Any differences in these factors affect the reliability of the results in comparative studies. Also, there is a lack of studies on lasers in darker skin types due to a higher incidence of adverse events.

In our study, 33 female patients with lower face hirsutism and Fitzpatrick skin phototypes III-V were randomly assigned to receive either triple-wavelength diode laser or IPL treatments to minimise bias. The mean percentage of hair reduction was significantly higher in the triple-wavelength diode laser group (74%) compared to the IPL group (46%) after one month of the fourth session [Figures 1a, 1b, 2a, 2b, 3a, 3b, 4a, and 4b]. Additionally, patients in the diode laser group experienced significantly longer hair regrowth intervals between sessions, and this interval further increased with subsequent treatments. At baseline, there was no significant difference in the absolute hair count between the two groups. However, a significant difference was observed in subsequent sessions, with the triple-wavelength diode laser group showing progressively lower hair counts compared to the IPL group across all sessions and after one month following the final treatment [Figure 5].

Close

Figure 1a:

Patient one – a 32-year-old female, pretreatment (right side: 10–15 hairs; left side: 10–15 hairs). IPL was performed on the right side, and diode laser on the left side.

Export to PPT

Close

Figure 1b:

One month after fourth sitting: hair density reduction is seen on both sides, but significantly more on the diode side (right side: 8–10 hairs; left side: 4–6 hairs).

Export to PPT

Close

Figure 2a:

Patient two – a 37-year-old female, pretreatment (right side: 8–10 hairs; left side: 10–12 hairs). IPL was performed on the right side, and diode laser on the left side.

Export to PPT

Close

Figure 2b:

One month after fourth sitting: hair density reduction is seen on both sides, but significantly more on the diode side (right side: 4–6 hairs; left side: 4–6 hairs).

Export to PPT

Close

Figure 3a:

Patient three – a 29-year-old female, pretreatment (right side: 12–14 hairs; left side: 15–20 hairs). Diode laser was performed on the right side and IPL on the left side.

Export to PPT

Close

Figure 3b:

One month after fourth sitting: hair density reduction is seen on both sides, but significantly more on the diode side (right side: 4–6 hairs; left side: 8–10 hairs).

Export to PPT

Close

Figure 4a:

Patient four – a 39-year-old female, pretreatment (right side: 8–10 hairs; left side: 15–20 hairs). Diode laser was performed on the right side and IPL on the left side.

Export to PPT

Close

Figure 4b:

One month after fourth sitting: hair density reduction is seen on both sides, but significantly more on the diode side (right side: 2–4 hairs; left side: 8–10 hairs).

Export to PPT

Close

Figure 5:

Line graph showing comparison of mean absolute hair count between IPL and Diode group- Paired t Test was applied (p value < 0.0001); mean absolute hair count was significantly lower at each sitting in the diode group compared to the IPL group.

Export to PPT

Transient erythema was reported equally in both groups. However, pain was reported by 11 patients in the diode laser group compared to 19 patients in the IPL group. These findings contrast with a study by Klein and colleagues who reported more pain in the diode laser group. Superficial burns occurred in four patients in the IPL group and one patient in the diode laser group; which were managed with a combination of topical antibiotic-steroid cream [Figure 6]. One patient in the IPL group developed secondary infection with Pseudomonas aeruginosa after a burn, which was confirmed on pus culture and treated with oral cefixime and topical gentamicin.

Close

Figure 6:

A 32-year-old female who developed a superficial burn on the of IPL treated side (right).

Export to PPT

Paradoxical hypertrichosis was reported in two patients from the IPL group, presenting as multiple vellus hair [Figure 7]. It is a known side effect associated with all laser types at low fluences. The risk factors include- thick and dark hair, underlying hormonal conditions, suboptimal fluence, and darker skin types III to VI. It commonly occurs in areas like the chin and neck and is observed in approximately 6-10% of laser hair reduction cases.⁷ We observed that the phenomenon occurred more in areas surrounding the treatment area. We propose that this could be due to dissipation of heat and inadequate cooling. The patients were managed by giving further sessions with higher fluence, shorter pulse duration, increased cooling, and stacking.^7,8 Moreno-Arias and colleagues also reported paradoxical hypertrichosis in five out of 49 females undergoing IPL treatment for facial hirsutism.⁹ Hirsch and colleagues also documented similar side effects in 14 patients treated with the long-pulse 755-nm alexandrite laser.¹⁰

Close

Figure 7:

A 20-year-old female who developed paradoxical hypertrichosis on the IPL treated side (left).

Export to PPT

Solid state lasers, such as long-pulsed Nd –YAG (1064nm) and Alexandrite (755nm) have demonstrated efficacy, particularly in darker skin types, owing to their longer wavelengths and greater depth of penetration. The largest clinical trial comparing three lasers- diode (810 nm), IPL (650 nm), and alexandrite (755 nm), was conducted by Toosi et al. on 232 persons.¹¹ The comparison of the treatment results after 6 months did not show any significant statistical difference between the three, although hair reduction was observed to be higher with the diode laser. Side effects were observed with all light sources, but more frequently with the diode.¹¹

Chen and colleagues conducted a similar study on 30 Asian patients with phototypes III and IV and dark, thick hair. They performed three sessions, spaced 6 to 8 weeks apart, using IPL on one leg and low-fluence diode laser on the other. However, after 12 months of follow-up, there was no statistically significant difference in effectiveness, treatment speed, or safety between the two methods.¹²

Klein and colleagues investigated 30 female patients with phototypes II and III, conducting six treatment sessions, four weeks apart, using a diode laser on one axilla and IPL on the other. After a 12-month follow-up, both treatments were found to be effective, safe, and long-lasting. However, the diode laser was more efficient and time-saving, though it caused more pain.¹³

Cameron et al.¹⁴ studied nine female patients with skin phototypes I to III, treating one limb with an 810 nm diode laser and the other with IPL over three sessions spaced six weeks apart. They concluded that the diode laser resulted in greater hair reduction than IPL.

Laser technology focuses energy on a single wavelength, while IPL disperses energy across multiple wavelengths, leading to significant light scattering and absorption in the epidermis, reducing effectiveness.⁶ IPL requires a high contrast between hair and skin colours, whereas diode laser does not.⁶

The use of shorter wavelengths in IPL, while offering greater melanin affinity and potential benefit in treating thin hair, also increases the risk of epidermal damage, thereby necessitating the use of cut-off filters above 650 nm for adequate epidermal protection. Thin hair, having shorter thermal relaxation time, require shorter pulse durations for effective treatment. Lasers offer greater adaptability in pulse duration, unlike IPL devices, which have limited adjustment options. Laser-induced erythema and perifollicular oedema are often absent with IPL, complicating parameter evaluation and precise placement. Additionally, IPL devices’ variability in fluence and wavelength between pulses can lead to inconsistent results.¹⁵

For patients with higher phototypes, diode lasers are more suitable due to their longer pulse durations (100 or 400 milliseconds) and the ability to use longer wavelengths with effective cooling mechanisms, minimising side effects. Conversely, IPL with its shorter, fixed pulse durations and shorter wavelengths, poses a higher risk and lower effectiveness in phototypes V and VI, but can be safely used in phototypes I to III and cautiously in phototype IV.^15,16 In our study, although the triple-wavelength diode laser demonstrated superior efficacy compared to IPL, however the side effect profiles of both modalities were comparable.

Limitations

The sample size was small with a short follow-up. Also we included patients with Fitzpatrick phototype III-V, so the results may not apply to all skin types.

Conclusion

From our study, it can be concluded that a synergistic combination of three laser wavelengths in a triple-wavelength diode laser (755nm, 810nm, 1064 nm) is effective and safe to use in subjects with facial hirsutism with Fitzpatrick phototypes III-V. Tripe wavelength diode laser (755nm, 810nm, 1064 nm) is more efficacious than IPL (690nm filter) in reducing hair density in patients with facial hirsutism. Nevertheless, both the modalities are equally safe.