Pediculosis (head, body and pubic lice) !
Infestation by lice, tiny insects that live on hair or clothing and feed on blood, causing itching. Head lice are very common in schoolchildren.
Updated 2026-11-01
Structures involved
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Microorganisms that cause it
What it is
Infestation of the human body by blood-sucking lice: the head louse (Pediculus humanus capitis), the body louse (Pediculus humanus corporis) and the pubic or crab louse (Pthirus pubis). Lice lay eggs (nits) glued to hairs or clothing fibres.
Who gets it
Head lice are common worldwide, especially in children of 3 to 11 years and in schools, and are frequent in Colombian schools; they are not a sign of poor hygiene. Body lice affect people living in crowded conditions without access to washing clothes, such as homeless people or refugees. Pubic lice are mainly sexually transmitted in adults.
Causes
- Head louse: spread by direct head-to-head contact, less often by shared combs, hats or pillows
- Body louse: lives and lays eggs in clothing seams and moves to the skin to feed
- Pubic louse: spread by sexual contact; can also infest eyelashes, eyebrows, beard and armpit hair
Risk factors
- School-age children and their families
- Crowded living, institutions and shelters
- Homelessness and lack of access to clean clothing (body lice)
- Multiple sexual partners (pubic lice)
Pathophysiology
Lice feed on blood several times a day and inject saliva while feeding. Sensitisation to the saliva and faeces causes itching, which may take weeks to appear after a first infestation. Lice cannot jump or fly and die within a day or two away from the host, while nits are glued firmly to the hair shaft near the scalp.
Classification
- Pediculosis capitis (head lice)
- Pediculosis corporis (body lice), a vector of epidemic typhus, trench fever and relapsing fever
- Pediculosis pubis (pubic or crab lice), including eyelash infestation
Symptoms and signs
- Itching of the scalp, especially behind the ears and at the nape of the neck
- Live lice and nits firmly attached to hairs close to the scalp
- Scratch marks, small red bumps and sometimes crusted sores
- Body lice: intense itching of the trunk with excoriations and, in chronic cases, thickened darkened skin
- Pubic lice: itching in the genital area and small blue-grey spots (maculae ceruleae) on the thighs or trunk
- Swollen lymph nodes in the neck when the scalp is infected
Diagnosis
- Clinical
- Diagnosis is made by finding a live louse. Wet combing with a fine-toothed lice comb is more reliable than looking alone. Nits further than about 1 cm from the scalp are usually empty and do not prove active infestation.
- Tests
- A magnifying lens or dermoscopy helps identify live lice and viable nits. In pubic lice, screening for other sexually transmitted infections (HIV, syphilis, gonorrhoea, chlamydia).
- Imaging
- Not needed.
Differential diagnosis
- Dandruff and seborrheic dermatitis (flakes slide off the hair, unlike nits)
- Hair casts and hair-spray debris
- Scabies
- Atopic or contact dermatitis
- Tinea capitis
Goal of treatment
Kill the lice and nits, stop transmission to close contacts and relieve itching, without using dangerous home remedies.
Treatment
- Medical
- Topical pediculicides such as permethrin or pyrethrins, repeated after about a week to kill newly hatched lice; alternatives include dimeticone, malathion, spinosad and topical ivermectin. Oral ivermectin for resistant cases.
- Conservative
- Wet combing with a fine-toothed lice comb every few days for two to three weeks; for eyelashes, a bland occlusive ointment and removal of nits.
- Lifestyle
- Body lice: bathe and change into clean clothes; wash clothing and bedding in hot water or seal them in a bag for two weeks. Never use kerosene, petrol or insecticides meant for animals.
- Follow-up
- Examine and treat household members and close contacts at the same time; children can return to school after the first treatment. For pubic lice, treat sexual partners and screen for other infections.
Drugs for this condition
Complications
- Secondary bacterial infection (impetigo) of scratched skin
- Louse-borne diseases from body lice: epidemic typhus, trench fever and relapsing fever
- Sleep disturbance, school absence and social stigma
- Skin irritation from overuse of pediculicides or unsafe home remedies
Prognosis
Excellent with correct treatment and combing, although reinfestation is common when contacts are not treated and resistance to some pediculicides is increasing.
Prevention
- Avoid head-to-head contact and sharing combs, hats or pillows
- Check and treat all household contacts at the same time
- Regular washing of clothing and bedding to prevent body lice
- Safe sexual practices and partner treatment for pubic lice
Test yourself
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How are head lice transmitted?
Mainly by direct head-to-head contact; lice cannot jump or fly, and pets do not spread them.
Which type of louse can transmit diseases, and which ones?
The body louse: epidemic typhus, trench fever and louse-borne relapsing fever.
Why is the treatment repeated after about a week?
To kill lice that hatch from nits that survived the first application.
What should a clinician consider when finding pubic lice in a child?
Possible sexual abuse; pubic lice on eyelashes in children may also come from adult contact.
Must a child with head lice be kept out of school until all nits are gone?
No; the child can return after starting treatment, and no-nit policies are not recommended.
Related conditions
Educational information, not medical advice. For any symptom, see a health professional.
Sources: About Lice | Lice | CDC (Centers for Disease Control and Prevention (CDC), 2026); Head lice | Pediculosis | MedlinePlus (MedlinePlus, US National Library of Medicine, 2026).
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