A Novel Nit Comb Concept Using Ultrasound Actuation: Preclinical Evaluation

Abstract

Nit combing and removal of head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae), eggs is a task made more difficult because "nit combs" vary in efficiency. There is currently no evidence that the binding of the eggshell to the hair can be loosened chemically and few hair treatments improve the slip of the louse eggs along the hair. Ultrasound, applied through the teeth of a nit comb, may facilitate the flow of fluids into the gap between the hair shaft and the tube of fixative holding louse eggs in place to improve lubrication. Ultrasound alone had little effect to initiate sliding, requiring a force of 121.5 ± 23.8 millinewtons (mN) compared with 125.8 ± 18.0 mN without ultrasound, but once the egg started to move it made the process easier. In the presence of a conditioner-like creamy lotion, ultrasound reduced the Peak force required to start movement to 24.3 ± 8.8 mN from 50.4 ± 13.0 mN without ultrasound. In contrast, some head louse treatments made removal of eggs more difficult, requiring approximately twice the Peak force to initiate movement compared with dry hair in the absence of ultrasound. However, following application of ultrasound, the forces required to initiate movement increased for an essential oil product, remained the same for isopropyl myristate and cyclomethicone, and halved for 4% dimeticone lotion. Fixing the nit comb at an estimated angle of 16.5° to the direction of pull gave an optimum effect to improve the removal process when a suitable lubricant was used.

Neem-silicone lotion and ultrasound nit comb: a randomised, controlled clinical trial treating head louse infestation

“…The benefits of using a comb with an angled head were demonstrated in laboratory tests (Burgess et al 2016) but not replicated clinically. The prototype was not ergonomic with a long, thick handle to accommodate batteries, which required effort to pull it through the hair.…”

“…Four treatment products were used: (Burgess et al 2016), which was the primary development objective of the whole project NNC and IPM/C were compared for efficacy against head lice when applied to dry hair until saturated. NNC was left in place overnight and then washed off with shampoo.…”

“…This device (Fig. 2) delivered ultrasound to the comb teeth through two piezoelectric actuators, as described previously (Burgess et al 2016). A fresh standard comb tooth unit (Innomed™ comb, Hogil Pharmaceutical Corp., White Plains, NY, USA) was fitted for each participant to eliminate any risk of cross-contamination.…”

“…A fresh standard comb tooth unit (Innomed™ comb, Hogil Pharmaceutical Corp., White Plains, NY, USA) was fitted for each participant to eliminate any risk of cross-contamination. Before the clinical work, the two lubricants were compared in the laboratory for their effect on loosening louse eggs (peak force) and sliding them along hair (average force), using a slip-peel tester (SP-2000, IMASS, Inc., Accord, MA, USA) as described previously (Burgess et al 2016;Burgess 2010).…”

“…Previously, we described a laboratory evaluation of the ultrasound comb, developed as part of this investigation, for facilitation of nit removal (Burgess et al 2016). In parallel, the neem oil-based lotion was reformulated to improve the activity against both lice and their eggs.…”