Montreal — There is evidence of how light or laser therapy may stimulate hair growth, according to Sunil Kalia, M.D., F.R.C.P.C., assistant professor, division of dermatology and skin sciences, University of British Columbia (UBC), Vancouver, who spoke here at a dermatology symposium about the facts and myths of laser and light therapy.
It is a rare side effect, but there is the possibility that patients can develop paradoxical hypertrichosis after a treatment like laser epilation, according to Dr. Kalia. The research focused on hair growth has looked at inflammatory markers or growth factors that may play a role in inducing hair growth. Most research looking at paradoxical hypertrichosis is retrospective, so the data should be interpreted with caution, Dr. Kalia says.
Still, patients’ expectations should be managed prior to undergoing laser treatment for hair removal, Dr. Kalia says.
"We should warn our patients that they could develop hypertrichosis if they are undergoing laser hair removal," Dr. Kalia says. "We don't fully understand the mechanisms of inducing hypertrichosis. The pathogenesis of hypertrichosis is not well-elucidated."
One study conducted by UBC clinicians looked at patients who had undergone laser hair removal with a long-pulsed alexandrite laser. A total of three of 489 patients (0.6 percent) had increased hair growth subsequent to laser hair epilation (Alajlan A, Shapiro J, Rivers JK, et al. J Am Acad Dermatol. 2005;53(1):85-88).
Dr. Kalia notes that patients with cutaneous porphyria can experience increased hair growth with exposure to light and that patients who have been exposed to psoralen ultra violet A also have experienced hair growth.
One of the modalities that has been studied to determine its ability to induce hair growth is low-level laser therapy (LLLT), which was first used in wound healing, Dr. Kalia says. LLLT uses wavelengths that are anywhere from 600 to 1,200 nm and involves ATP (adenosine triphosphate) synthesis, causes reactive oxygen species to develop, the stimulation of growth factors, leading to an increased amount of hair growth, Dr. Kalia says.
One investigation looked at the impact of the HairMax LaserComb (Lexington International), a LLLT, as an avenue for hair growth and cessation of hair loss in men with androgenetic alopecia. Dr. Kalia says that the investigation found patients in the treatment group experienced a greater increase in mean terminal hair density compared with those exposed to the sham device group, p<0.0001. The therapy was also found to be safe with no serious side effects reported (Leavitt M, Charles G, Heyman E, Michaels D. Clin Drug Invest. 2009;29(5):283-292).
"However, the majority of patients in the study reported no growth or minimal growth," Dr. Kalia says of the findings of the research.
Low energy exposure has also been studied with women having female pattern hair loss. Dr. Kalia cites a study of 28 women in South Korea, where women with female pattern hair loss were treated with a 1,550 nm fractional erbium-glass laser for five months. There was a marked increase in hair density and hair thickness after 10 treatments. Photographs indicated global improvement in the majority of patients. A couple of patients experienced transient pruritus which resolved (Lee GY, Lee SJ, Kim WS. J Eur Acad Dermatol Venereol. 2011;25(12):1450-1454).
Given the study was only six months, the long-term effects of the therapy are unknown. Another important limitation of the study was the absence of a control group. "We don't have a control group to compare the patients to," Dr. Kalia says.
Overall, light energy can stimulate hair growth, but with LLLT, parameters like wavelength, pulse duration, and fluence remain unknown in terms of optimizing treatment, Dr. Kalia says. Further studies are required with LLLT.
There are new light technologies that are currently being studied, and the data from those studies should be available in the future, Dr. Kalia adds. Studies comparing light and laser therapies to standard hair loss treatments like minoxidil and androgen inhibitors should be conducted, Dr. Kalia says.
In daily practice, when dermatologists are communicating with patients, it's important that dermatologists manage patient expectations, so patients do not anticipate seeing dramatic changes on the scalp in hair growth after treatment, according to Dr. Kalia.
Disclosures: Dr. Kalia reports no relevant financial interests.