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Head lice are small, flat, six-leg, blood-sucking, wingless insects about 2–4 mm long that live, reproduce and feed on the human scalp. Head lice have been surviving in humans for millions of years and are a pervasive problem. These are transmitted from person to person by direct contact, lice cannot jump or fly, and they can only crawl. Head lice are transmitted only from human-to-human only. Cats, dogs, and other pets do not have any role in human lice transmission. Spotting lice in hair is not always easy because sometimes you may not feel any symptoms. Adult lice make you feel like moving something in your hair and itchy. When you are infected with head lice, then you should focus on treating yourself. Entire house cleaning or sanitization is not required. Anyone may get head lice when coming in contact with an infected person. Head lice problem is common among elementary and preschool school-age children and their house members. Therefore, you should check your children’s hair weekly to keep a close check on head lice.[1-5]

Stages

As we learned above, head lice feed on the human scalp and complete the life span of the human scalp by going through the various stages of its life. There are three stages in the life span of the head lice described below:[3,5-7]

Eggs

Eggs are also known as nits. Lice lay their eggs on the hair strands that are firmly attached to the hair. Eggs are small like sand grain, yellow oval, tan or whitish-grey. Eggs usually hatch in 9 to 10 days. Eggs are 0.8 mm by 0.3 mm in length.

Nymphs

When the egg hatches in about 9 days, they release a nymph. Nymphs look like adult lice but are smaller in size than adult lice. Nymphs also remain attached to hair strands. Nymphs then mature and become adult lice, approximately seven days after hatching.

Adult Lice

The colour of adult lice is white, dark grey or brown. Female adult lice are longer than male adult lice. The size of the adult lice is similar to the size of a sesame seed. Each night, female lice lay 7–10 eggs per day. The life span of a louse is 30 days. Lice can remain alive only for 2-3 days after detaching from the human hair. To remain alive, adult lice suck blood several times from the human scalp. During the life span of a female head louse, it produces around 140 eggs.

Symptoms

Below are the symptoms that you may feel when having head lice:[5,8]

• If you have head lice, it might be possible that you do not feel any symptoms. But the common symptom of head lice is head itching, especially where the lice are more likely to live, i.e., on the back of the neck, head and near the ears.


• This itching is due to the allergic response by your body against the lice bites. Itching is not caused instantly when you get the lice in your hair; it takes 4 to 6 weeks to appear.


• Other symptoms may include a feeling of something moving on your scalp.


• It may cause sleeplessness and irritation.


• Sores on the scalp due to scratching are another common symptom.

Prevention

The onset of lice in your hair can not be prevented, but you can stop their transmission from person to person:[8]

• Do not share brushes, combs, hats or towels with others.


• Avoid coming in physical contact with someone who is having lice.


• You should not use medicated sprays and lotions unnecessarily to prevent lice, as this can irritate your scalp.


• Instead of stopping the children from going to school, inform the school that your child has lice.


• You should avoid head-to-head contact during play, at parties, and while playing game activities.


• Avoid using fumigant fogs or sprays; they are not essential to control head lice and may be toxic if absorbed via the skin or inhaled.


• If you have used chemicals to treat the lice, then wash the touched clothes, pillows etc. properly with hot water. The things that cannot be washed should be dry cleaned and stored for 2 weeks after sealing in a bag.

Diagnosis

By looking closely, you can easily find the lice in hair or tiny eggs firmly attached to the hair strand. Eggs are very similar to dandruff, but they are tough to brush.

To be sure that you have lice, you have to find live lice. It might also be possible that you have only eggs on the hair strand and adult lice. You have to part your hair into small sections and then move through hair from one side to another side. Check carefully.

To find the lice or egg, lighting should be proper. As lice move very fast and are hard to find, you should keep a very close eye on the back of the ear and backside of the head.[6]

Treatment

When you spot live in your hair, try to get rid of them as soon as possible, unless these will grow at a very fast rate in your hair. You can get rid of them without consulting a doctor. When you find the lice in your hair, all family members should also check and start treating the head lice from day 1.

Below are some treatment methods to get rid of head lice:

• Wet Combing: The method that you try first is wet combing. Both eggs and lice can be removed with wet combing. The procedure for this method is: wash your hair with any shampoo, then apply lots of any ordinary conditioner, wash hair properly and then comb your hair from the roots towards the end of the hair. For short hair, 20-minute wet combing is sufficient and for long, curly, or frizzy hair, you can try for 20 to 30 minutes. Wet combing should be done after 3 to 4 days for 17 days.


• Medicated Sprays and Lotions: If you have already tried wet combing for 17 days but not getting relief from head lice, then ask a pharmacist for help. The pharmacist will recommend medicated sprays, shampoo or lotions that kill the lice in the head. These products are also available online or in supermarkets. These sprays o lotions can kill all head lice in one day. Some sprays or lotions also provide a comb to remove eggs or lice from the hair. Some of these treatments are required to be repeated after one week to kill the newborn lice. With most of these treatment products, you will find a leaflet that guides you on using the product.[4]

Below are the over-the-counter chemicals that kill lice:[6]

• Permethrin - is safe to use in humans.


• Pyrethrin - is safe to use in humans.


• Lindane - can be toxic, and should not be used in children younger than 2 years of age.

The method to use these chemicals is given below:

• You have to follow package directions carefully.


• Do not leave the shampoo on hair for longer than directed.


• After the treatment, rinse the hair well with water. It is best to wash the hair over a sink so that other body parts do not come in contact with the product.


• Repeat the treatment after one week or 10 days.

Complications

There are no direct complications due to lice; but if you scratch the scalp intensely, then the scalp skin can be injured and cause infection and open sores. Head lice, if left untreated, may cause scalp pruritus (the irritating sensation that provokes an urge to scratch the scalp), impetigo (bacterial skin infection), furunculosis (deep hair follicle infection), or scalp pyoderma (pus-filled acne).[7,8]

References

1. Paediatr Child Health. 2008;13(8):692-704.

2. Head lice (nits). Better Health Channel. Available at: https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/head-lice-nits#treatment-for-head-lice.

3. Head lice. Ministry of Health Manatu Hauora. Available at: https://www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/head-lice.

4. Head lice and nits. NHS. Available at: https://www.nhs.uk/conditions/head-lice-and-nits/.

5. Head Lice. CDC. Available at: https://www.cdc.gov/parasites/lice/head/prevent.html.

6. Paediatr Child Health. 2008 Oct;13(8):697-706.

7. H.Feldmeier. Academic Press. 2008. Pages 282-294.

8. Head Lice. Cleveland Clinic. Available at: https://my.clevelandclinic.org/health/diseases/10824-head-lice#symptoms-and-causes.