Infestations that itch - head lice & scabies - Column

Pediatrics for Parents, March, 1994 by Harry Pellman

Head Lice

The louse is tiny insect about 1-2 mm. long. Lice are territorial in that head lice only live on the scalp, body lice on the body, and pubic lice in the pubic region. These little bugs take time off from their busy, egg-laying career to frequently bite the scalp and have a blood meal. The bites produce a small, itchy bump on the head. The eggs are laid on the hair shaft very close to the scalp. The eggs, referred to as nits, look like miniature wax tear-drops and are cemented to the hair shaft. They hatch in about a week and the eggs are about 1/2 inch from the scalp at this time.

Head lice are not picky. They like all hair -- clean, dirty, blond, black, short, long, ratty, tatty, and spaghetti. Lice also do not discriminate on a socioeconomic level and infect the rich as well as the poor. However, they do racially discriminate and infect African Americans much less frequently. Head lice is most common in preschool and school age children. This age group likes to share, especially combs, brushes, hats, and, of course, diseases.

Like a fish out of water, lice do poorly when not cruising on someone's scalp. They only survive a day or so off the head. Their eggs survive a week or less when removed from the scalp.

The diagnosis is suspected in a child frequently scratching the scalp. It is confirmed by either finding adult lice on the scalp, or, more easily, observing the typical waxy, tear-drop-shaped eggs on the hair shaft. The hair most frequently involved is at the nape of the neck, the crown of the head, and over the ears. A bright light and magnifier facilitates this chore. In addition, wetting the hair and rubbing the scalp with a towel irritates the little critters and sets them into motion, again facilitating their detection. The eggs are sometimes difficult to differentiate from dandruff or hair casts. The latter flake off the hair easily while eggs are firmly cemented onto the shaft. In addition, eggs are homogeneous in shape and size, unlike dandruff and hair casts.

Prevention begins with an appropriate hygiene policy. Discourage sharing of combs and brushes. Assign separated coat hooks or lockers for children's coats, sweaters, sweat shirts, etc. Children should sleep and nap in separate beds if possible.

Infected clothing, bedding, and washable toys are sterilized by machine washing and drying in hot cycles or by dry cleaning. Storing infected objects in a sealed plastic bag at room temperature for 14 days sterilizes these items. Combs and brushes are disinfected by soaking in hot, soapy water for 10 minutes.

Examine other family members and contacts. Those identified with head lice need treatment to prevent reinfection. Close contacts, such as other family members, are often treated regardless of finding signs of head lice.

The most effective and safest treatment is one percent permethrin creme rinse, an over-the-counter preparation. After shampooing, all family members apply the 1% permethrin creme rinse. After ten minutes, the creme rinse is washed off. This kills all adults and most fertile eggs. A medicine residue is present on the hair shaft for about two weeks and helps prevent reinfection. Other available preparations are either more toxic, less efficacious, or need two treatments.

Even with this therapy some eggs may survive. Therefore, for best results, eggs need to be rmoved from the hair shaft. Eggs more than 1/2 inch from the shaft have probably hatched and are unlikely to be infective. Picking out individual eggs by the fingernail method is quite laborious (thus the term nit-picking). The easiest way to remove the cemented eggs is to first soak the hair in vinegar for 30-60 minutes. Alternately, a commercial rinse, Step 2, is available. These products help loosen the cement. Use a fine-toothed, special lice comb, usually supplied with commercial lice treatment products, to comb out remaining eggs. Children may return to school the day following appropriate treatment.

Scabies

Scabies is a human infestation caused by the human mite, Sarcoptes scabeii (hominis). After contact with this critter, it finds a cozy location, burrows under the skin, and sets up housekeeping. In this location it eats, sleeps, and defecates. In 4-6 weeks, the child develops a reaction to this foreign intruder and its body parts. The small bumps that house the mite become itchy, often intensely so. This is frequently followed by a general allergic reaction that produces itchy bumps all over the body. These "allergic" bumps house no mites.

The skin areas most frequently involved are the tops of the fingers and wrists, skin folds, elbows, armpits, belt line, genital region, buttocks, and the sides of the feet. In addition, in children under 1 or 2, the bumps may resemble blisters and may even involve the head, neck, palms, and soles, very unusual locations for older, healthy children. Children with immune deficiency may develop severe scabies with sores teaming with large numbers of mites.

Scabies is very contagious. Transmission occurs by contact with an infected person. Human scabies is a human-only disease except for the occasional puppy dog scabies. In this situation, a newly arrived puppy with dog mites (mange) transmits these critters to a family child who frequently hugs the canine. The few bumps the child develops in this situation are self limited since the dog mite cannot reproduce on the human.