I am a geek, so my light reading often extends to the scientific journal Medical and Veterinary Entomology, published for the Royal Entomological Society. And I take great delight in bringing you the latest nit news from the arcane world of academic entomology.
Phthirapterists (people who study lice) are an inventive bunch. Not only do they keep lice as pets (more on that later), they build nit-testing machinery. The latest offering is a gadget to test how easy (or not) it is to slide a nit from its cemented position on a hair stalk.
Nit glue is pretty tough stuff, and is one of the secrets of louse success. It is created by the female louse as a liquid, but hardens within seconds on exposure to air. It forms a tight sheath around the hair stalk which holds he egg in place with a vice-like grip. Long after the tiny louseling has hatched and walked off across the scalp, the empty eggshell (nit), now bright white, is a brilliant distraction to focus our grooming on the wrong things. Months after the louse has left its egg, the nits are still firmly attached to the hair, and as the hair grows the nits just become more obvious.
Since some schools operate a no-nit policy, parents can spend hours of wasteful time trying to get rid of them. Any pharmaceutical company that comes out with a nit-glue-dissolving preparation will be on to a winner. But I’m not convinced. The cement appears to have a chemical structure somewhat similar to hair. If a chemical can dissolve the glue, surely it will surely dissolve the hair too. The trouble is that these chemical companies can get rather carried away with the advertising claims.
Ian Burgess, at the Medical Entomology Centre in Cambridge, put some of their claims to the test. He developed a machine with a tiny glass tube through which a nit-laden hair was passed. The tube was so small that the hair could just get through, but the nit could not, and was held fast at the tube entrance. He then measured how much force was required to pull the hair through the tube, and free from the louse egg.
He tried several specialized nit-loosening brands, along with some anti-louse shampoos, ordinary hair conditioner, olive oil, plain water and dry hair. And this is what he found:
“We conclude that so-called ‘nit-removing’ products have no effect in terms of loosening the grip of the cement-like fixative secreted by the female louse to hold her eggs in place on the hair. None of the products tested demonstrated any detectable chemical or physical activity beyond lubricating effects indistinguishable from those found for widely used toiletry or cosmetic products….There appears to be no justification in purchasing products specifically marketed for this purpose.”
In other words, they don’t work. Told you so.