Evaluation of a hot-wire hair removal device compared to razor shaving

We describe a blinded, controlled, prospective clinical study of a hot-wire device promoted for hair removal and the reduction or delay of hair regrowth (no!no!, Radiancy, Inc., Orangeburg, NY) compared to a shaving control.

Twenty-two subjects were treated by trained clinical staff with the hot-wire device according to its Instructions for Use on the lower leg two times per week for 8 weeks. An adjacent site was shaved with a razor blade on the same schedule to provide a control. Subjects were followed for 3 months after the last treatment to study the durability of the results. Standardized high-resolution photographs were made at baseline, once a week during treatment, and monthly during the post-treatment follow-up period. Micro-tattoos were used to ensure treatments and photographs were reliably made in the same anatomical location from visit to visit. Both active and control sites were shaved prior to baseline and allowed to regrow for a fixed period of time before first treatment to provide a consistent and well-defined baseline hair condition. Quantitative hair counts were made by a third party from the photographs and standard statistical analysis was performed to look for differences between the active and control sites. Visual assessments and quantitative analysis was also performed on the photographs to see if there were any differences in hair thickness (diameter) and hair color between the active and control sites.

The results show that shaving and the hot-wire device are indistinguishable in short-term or long-term effect, based on both visual assessment of the photographs and statistical analysis of the hair counts. The control (shaving) had a mean baseline hair count of 79.4, which remained stable (74.8-84.3) during the 8 week-treatment phase and climbed substantially after stopping treatment to 98.8, 100.1, and 104.6 at 1, 2, and 3 months post-treatment, respectively. The active (hot-wire device) had a mean baseline hair count of 86.0 which remained fairly stable (81.7-95.1) during the treatment phase and then climbed substantially after stopping treatment to 104.0, 106.4, and 109.0 at 1, 2, and 3 months post-treatment, respectively. The difference in hair counts between the control and shaving showed that (a) in the treatment phase, shaving was slightly more effective at hair removal than the hot-wire device with weak statistical significance (P < 0.05 at 5 of 7 time points) and (b) in the follow-up phase, shaving and the hot-wire device were statistically indistinguishable (P = 0.252, 0.0972, and 0.230 at 1, 2, and 3 months, respectively). Likewise, the difference in percentage change from baseline in hair counts (which normalizes to baseline values) between the shaving control and hot-wire device is close to zero at every time point (-4.9% to +4.9%) and the t-test P-values are high (0.154< P < 0.890 over all the time points in the study and 0.360 < P < 0.890 during the 1, 2, and 3 month follow-up period), indicating no detectable difference between shaving and the hot-wire. In terms of hair characteristics, no difference in hair color or hair thickness was seen between the shaving control and the hot-wire sites in the treatment or follow-up period.

Relative to shaving, the hot-wire (no!no!) device does not produce lessened hair density, decreased hair re-growth rate, greater duration of effect, nor induce changes in hair thickness and color. We conclude that the hot-wire device does not offer any benefit as compared to shaving.