Head lice facts
Head lice are wingless insects measuring 2.0 to 3.5 mm, that live in hair only on the human head. They can especially be found behind the ears and in the neckline at the back of the neck.
Lice can not jump or fly but spread when direct hair to hair contact occurs, using their six very powerful legs with hook-like claws.
Transmission takes place from human to human, objects such as commonly-shared caps, hair brushes and toys which come into contact with scalp hair are rarely the cause for transmitting head lice.
Schools and daycare
The head lice problem seems to be persisting in the daycares as children often play in proximity to each other. Lice moves from one person’s scalp hair to the other when the heads of the children are in proximity. One big reason for that is due to increased resistance of lice to old treatments containing insecticides that have neurotoxic mode of action. Some of these treatments do not kill the nits (eggs) and the lice keep coming back again and again and they also spread from one child to the other. With the availability of NYDA® , you now have a solution that is not only effective against head lice and larvae but also eliminates eggs (nits). The good news is that it has a physical mode of action that prevents development of resistance. The mode of action kills eggs and head lice through suffocation.
Life Cycle of Head Lice & Eggs
The head louse develops in three stages: egg (nit), larvae or nymph (1-2 mm long) and adult.
When treating head lice infestations, it is essential to effectively combat the lice at all stages of development, i.e. the adult louse, larvae and eggs (nits) to make sure that you eradicate the problem.
The cycle from egg to adult (i.e. capable of producing its first batch of eggs) is generally around three weeks. Their development is dependent on environmental temperature and humidity. The optimum temperature for the development of lice is 32°C.
Using a water-insoluble ‘glue’, the adult female attaches the oval 0.8 mm-long eggs (nits) onto the hair shaft, close to the base of the hair. The eggs are encased in a shell of chitin. It then takes 7-8 days for the larvae to hatch.
Adult lice emerge from the larval stage within 9-12 days and are then ready to reproduce after a further 2-3 days.
Main Symptoms of Head Lice
Head lice suck blood several times a day, during which they inject an anticoagulant saliva into the scalp. This triggers off the main symptom associated with head lice infestation, i.e. persistent itching.
After initial infestation, it can often take up to several weeks for the immunologic reaction to appear. First of all, red papules become visible on the scalp, which may be followed by nettle-like reactions. Itching increases with the number of bites.
Scratching the bites may allow bacteria to enter, thereby making skin reactions even worse.
Current Treatments & Issues
Although other head lice treatments are also available, their main issues and limitations include the following:
Resistance
- Resistance to neurotoxic mode of action products is one reason for persistence of head lice.
- Resistance to head lice treatments has become a growing concern for healthcare professionals, educators and parents and a social annoyance and discomfort for patients.
Safety
- Some current treatments available contain neurotoxic mode of action chemicals.
Efficacy
- Some head lice products may only kill adult head lice and nymphs but to a lesser extent, not their eggs (which can survive and later develop into adult head lice and reinfest).
- Worldwide head lice are becoming increasingly resistant to neurotoxic mode of action pediculicides.
Application & Use
- Most treatments in the market do not come with any application aid.