The following notes were taken by Susan Devenish Mutton MIT IAT at the Institute of Trichologists Professional Development Seminar for members and students in November.
Ian Burgess – of the Medical Entomology Centre - Insect Research and Development gave a very good account of the subject Keeping one step ahead of lice
There is often poor knowledge of louse biology and in some cases the information in scientific articles is incorrect.Some products bought to clear the problem do not do what they say on the pack. Most products claim to kill, but they do not.
There was a rise in the numbers of head lice affecting this Country when in 1994-1996 a Department of Health leaflet suggested that combing was the best way to deal with it. Statistics now prove that this was incorrect, and more head lice survived to grow and spread, at that time.
The mother louse will deposit 3 to 5 eggs per day, the nit is the shell left behind. Males hatch more quickly at seven days and females in nine days. There are transmission stages when young nymphs (babies) stay close to the scalp and rarely move. As they get older young adults move on and the males move more rapidly than females as they look out for new mating opportunities.
The people at high risk to gain head lice are those with lots of best friends who are continually in contact and making it easy for the transfer from one head to another by touch. The person who is isolated and not mixing and making contact physically with others will be the person who will be most likely to build up large numbers and will not pass them on to others very quickly.
It has been a battle for 60 years with the early form of treatment being shampoo that has been utterly useless. The lice and eggs have survived and some reject insecticide. Sprays do not kill eggs, they survive and nymphs are selected for resistance. DDT was used in the 1950’s – 1970’s. Reasons for failure to wipe them out points toward poorly formulated products and that these are not left on for long enough and the fact that wet combing methods have not been successful. (Only plastic dissection combs are suitable for wet combing method and metal combs useless) It is also advised that children produce enough sebum on the scalp and do not need hair conditioners.
In his studies it has been found that not enough product is prescribed and therefore not enough is used by the patient and their family. The reproduction cycle is all important and the treatment must be repeated after one week. A 50ml, minimum, application is advised for short hair and 200ml per application for long hair. Therefore, a family with two children who have thick long hair and parents with short thick hair would probably need 500ml for the first and 500ml for the second application.
The advice is to detect the condition early, use better/effective products and to apply treatment and repeat 7 days apart. Hedrin lotion is recommended, it has an active product of 4% dimeticone. It will dry within an hour and has no colour or odour, and is non- irritant. The viscosity of the product is all important as it works by encapsulating the lice in a plastic layer of dimeticone – they become shrink wrapped and consequently can no longer drink the blood of their host or carry out their all important ‘transpiration’ method of expelling moisture. Temperature and humidity is their life line.
In conclusion, a product left on for ten minutes will be useless, instructions must be followed, and the key to success is to apply the stated amount of Hedrin, no less, and leave for the recommended length of time, at least eight hours - shampoo – rinse well, and repeat seven days later. Even then a plastic ‘nit’ comb may be required to scrape the empty cases/nits that are adhering to hairs.
'Trichorrhexis nodosa – rupture of the cortex.'