Lethal Effects of Treatment with a Special Dimeticone Formula on Head Lice and House Crickets (Orthoptera, Ensifera: Acheta domestica and Anoplura, Phthiraptera: Pediculus humanus)

Abstract

The present study provides the first convincing explanation of the mode of action of the medical device NYDA, a special dimeticone (CAS 9006-65-9) formula containing 92% of two dimeticones with different viscosities specifically designed for the physical treatment of head lice infestations (pediculosis capitis) by suffocation. Both, lice (Pediculus humanus) and house crickets (Acheta domestica) treated with this anti-head lice product are knocked out to the status "of no major vital signs" within less than 1 min that in consequence is accompanied irreversibly with the death of the respective insects. Scanning electron microscopical investigations have revealed that the cuticle is coated by a thin closed layer of the dimeticone formula that also enters the stigmata. In vivo observations and dissections of Acheta domestica have shown that application of the medical device to the thoracic stigmata invariably leads to rapid death; this is strongly correlated with the influx of the special dimeticone formula into the head trachea, whereby the solution effectively blocks the oxygen supply of the central nervous system. Dissections after application of the stained product show that it also enters the finest tracheal branches. Analogous in vivo observations in Pediculus humanus have confirmed the correlation between the disappearance of major vital signs and the displacement of air by the dimeticone formula in the tracheal system of the head. For both insect species, statistical data are provided for the chronological sequence of the filling of the tracheal system in relation to the respective vitality conditions of the Insects. On average, the special dimeticone formula reaches the insect's head tracheae within 0.5 min in house crickets and in less than 1 min in lice with a complete filling of the entire head tracheal system of lice within 3.5 min. In addition, a timed sequence of images illustrates this process for lice. The experiments clearly reveal the exclusive and pure physical mode of action of the tested dimeticone formula.

A Review on the Mode of Action and Current Use of Petroleum Distilled Spray Oils

“…Spiracle blockage has also been observed and documented when using other products with similar physical characteristics as insecticide oils. Richling and Böckeler (2008) observed a similar phenomenon when treating Pediculus humanus Haeckel, (Phthiraptera: Pediculidae) and Acheta domestica (Orthoptera: Gryllidae) with low viscosity silicone. When the insect was immersed in or coated with silicone, the fluid entered all spiracles equally and systematically flowed through the tracheal system and completely filled the trachea in the insect's head in less than one minute.…”

Comparative efficacy of new commercial pediculicides against adults and eggs of Pediculus humanus capitis (head lice)

“…), the hair tuft test showed a 100% of mortality on motile forms. As the treated lice were immobile almost immediately, it appears that it was due to the physical action of the silicones that coated the louse surface and enters through the respiratory tract, blocking either spiracles or tracheae (Richling and Böckeler 2008;Burgess 2009). The ovicidal activity of commercial products is summarized in Fig.…”

Ovicidal efficacy of high concentration dimeticone: A new era of head lice treatment

“…a vehicle for the other dimeticone component of higher viscosity, facilitating entry into the aeropyles of eggs, similar to its entry into the spiracles of lice. 3 Previous studies have shown efficacy of this product against adult lice, 4 and in a clinical trial, efficacy was superior to 1% permethrin in aqueous suspension. 1 The reasons for the low ovicidal efficacy of the 4% dimeticone are not clear.…”