Head lice are very small, wingless insects which cling to hair and are usually found on the scalp. They are grey-brown in colour and about 2.5mm long. They cannot fly, jump or swim and spread by ‘head-to-head’ contact.
Head lice live off blood obtained by biting into the scalp of the host. They are not dangerous and do not spread disease. However, it is wise to treat head lice quickly as they spread very easily from one scalp to another.
Female head lice lay eggs and cement them to hairs, often near the root of the hair follicle where they are kept warm by the scalp. These head lice eggs are called nits. They are approximately the size of a pinhead and very difficult to spot.
It takes seven to ten days for head lice eggs to hatch and as soon as they do so, baby head lice begin to feed. It takes seven to ten days for the lice to become fully grown and only when the louse is mature can it transfer to the head of a different host.
Female lice start to lay eggs as quickly as seven days after they are born. So, it is important that any head lice treatment is repeated in a six day cycle.
Lice eggs (known as nits) are laid at the root of the hair to stay warm. They are yellow, tan or brown in colour and look similar to dandruff. Head lice eggs cannot be removed easily by brushing or shaking.
It is more common to see nits in hair than actual head lice as they are easier to spot. Once head lice hatch, the empty shells of nits turn a white or clear colour and remain attached to the hair shaft.
Head lice often cause the scalp to itch because head lice bites give rise to irritation. Some people may take an allergic reaction to the lice and this leads to more scratching.
However, some people do not react to the bites from head lice and it could be up to two or three months before symptoms of head lice appear. In these cases, a rash may be seen on the back of the neck, caused by louse droppings. Excessive scratching around the area of the rash or bitten areas could also lead to a bacterial infection.
Head lice are most common in children between the ages of four and eleven and infestations seem to peak at the start of each primary school term.
Lice cannot be passed around by pets such as cats and dogs. They can only be transmitted by head to head contact as they cannot fly, jump, swim or hop. Therefore children playing or families embracing each other at home provide ideal opportunities for head lice to spread.
It is a common misconception that head lice only live in dirty hair. Poor hygiene has nothing to do with how lice are spread and it is equally likely that you will find head lice living in clean and dirty hair.
The first step in the treatment of head lice is to detect them. Parting the hair to look for head lice will not help in detection as the lice very quickly move into hiding. However nits may be seen at the root of the hair.
The most effective way of detecting head lice is to use a head lice comb - a very fine toothed plastic comb with less that 0.3mm spacing. Getting your child to lean over a bit of light coloured paper as you use the comb will help you see live head lice and nits as they fall out of the hair.
To ensure that you examine every section of the scalp, use a system for combing. For example:
- Detangle hair with an ordinary brush or comb
- Start at the middle of the front of the scalp with the detection comb
- Ensure that you comb from the roots to the very ends of the hair
- After each stroke examine the comb for head lice and nits, then rinse with water before the next stroke
- Continue combing each section till the whole head of hair has been examined
There are many different types of treatment for head lice. However no single method is 100% effective:
- Insecticides can be obtained from a pharmacy in the form of head lice lotions or shampoos. However it is very easy to use these products in the wrong way and if so, resistance may form and these chemicals will then have very little effect on the head lice
- Silicon-based products can be effective in treating head lice. They do not poison the parasites by chemicals but coat their surfaces and smother them. As they work physically, the parasites cannot develop a resistance to these products, but you will have to use the comb to remove head lice and nits
- Wet combing enables you to remove head lice and nits without applying chemicals. It is a simple method for treating head lice and does not have any side effects. Wash and condition the hair, then comb it through every third or fourth day for a two week period
- Herbal head lice treatments are gaining in popularity.
Head lice infestations are not very easily prevented. Regular combing will allow you to detect and remove head lice quickly. Using specific shampoos or lotions will not prevent head lice or nits as these can only be treated once they are present in the hair.
However you can warn children to avoid head to head contact at school, not to share combs, hats, scarves etc. Do not let children lie on bedding, pillows or carpets that have been used by someone who has recently had lice.
If a child has picked up head lice, treat every member of the family as it is likely that head lice will have passed from one to another through close personal contact.
Head lice are becoming resistant to the synthetic products commonly used to control them. These products contain pyrethroids and organophosphates, which are potentially harmful to put on the skin (especially the scalp which absorbs these substances well). The use of organophosphates, in particular, has been connected with adverse effects such as depression.
Lice are skilled at adapting to resist toxic chemicals. They can’t, however, become resistant to natural based treatments.