Head lice: impact of COVID-19 and slow recovery of prevalence in Cambridgeshire, UK.

Following school closures and changes in contact behavior of children and adults a reduced head louse prevalence has been reported from across the globe. In parallel, sales of treatments were observed to fall, partly because of supply problems of some products following the pandemic, but this did not appear to result in more cases of infestation. Surveys of schools in and around Cambridge, UK, found that infestation rates were significantly reduced particularly in city schools compared with similar surveys conducted before the COVID-19 pandemic. Contrary to expectation the number of cases in schools has only risen slowly since schools returned to normal full time working in 2022-2023.

Head louse egg and nit remover-a modern "Quest for the Holy Grail".

BACKGROUND: The eggs of head lice are fixed to the hair of their hosts by means of a persistent glue-like fixative that is not chemically bound to the substrate. Eggshells stuck to hairs after successfully treating the infestation are a cosmetic issue and a source of misunderstanding about whether the infestation is eliminated. Hitherto, no effective treatment to loosen louse eggs and nits has been found. METHODS: An extensive screening of surface active compounds, oils, esters, and other cosmetic lubricants used a slip-peel device to measure the forces required to release the grip of the fixative. Promisingly effective compounds were formulated into suitable carriers for further testing. The most effective combination formulation was tested, as a commercial product (Hedrin Stubborn Egg Loosening Lotion), in a usage study of 15 children with nits, in which one half of the head was combed only on damp hair and the other half combed after a 10 min treatment using the product. RESULTS: Laboratory tests of the forces required to remove nits found that pelagonic acid derivatives, particularly isononyl isononanoate, in the presence of a polymeric gelling agent and water, were most effective to reduce the initial grip of the fixative as well as reducing friction as the eggshell is drawn along the hair shaft and that the final product was significantly (p < 0.05) more effective than several other marketed materials. In the usage study significantly (p = 0.01046) more louse eggs and nits were removed after treatment with the gel. DISCUSSION: The product developed through this study is the first with a demonstrable efficacy for loosening the grip of the louse egg fixative from hair. Consequently, until now, and despite the availability of effective pediculicidal treatments, dealing with the eggshells persisting after an infestation has been an onerous task for most households. This type of product can enable families to deal more easily with persistent eggshells and improve self-esteem in affected children.

A Novel Nit Comb Concept Using Ultrasound Actuation: Preclinical Evaluation.

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.