Pediculosis
Pediculosis is a common infestation of human skin and hair by lice, small wingless insects that live as ectoparasites. Unlike ordinary biting insects, lice depend entirely on a human host and must feed on blood to survive. Although lice are not directly life-threatening in the way strongyloides hyperinfection syndrome can be, they cause intense itchy inflammation, lost sleep and real distress for children and parents, and scratching easily leads to secondary impetigo from bacterial infection.
At Haute-Derma, managing lice starts with accurately distinguishing viable nits from dandruff or hair casts. We then use newer-generation treatments that kill lice by a physical mechanism (sidestepping drug resistance) and give families and schools clear guidance on controlling spread.
How Lice Cause Disease and How They Spread
Types of Lice
Three species of the order Phthiraptera infest different parts of the body:
- Head louse (Pediculus humanus capitis): The most common species, living mainly on the scalp and hair, especially behind the ears and at the back of the head.
- Body louse (Pediculus humanus corporis): Lives and lays eggs in the folds and seams of clothing, moving onto the skin only to feed. It can transmit systemic infections (epidemic typhus caused by Rickettsia prowazekii, and relapsing fever).
- Pubic or crab louse (Pthirus pubis): Infests pubic hair, underarm hair, and the eyelashes and eyebrows.
Life Cycle and How Lice Damage the Skin
- Feeding: Adult lice pierce the scalp with their mouthparts and feed 4–5 times a day, injecting saliva that contains anticoagulants and enzymes.
- Allergic reaction: Louse saliva triggers a hypersensitivity response (type I and type IV), producing intense itching that starts days to weeks after the first infestation.
- How nits hold on: A female louse lays 6–10 eggs a day. Each egg is coated in a waterproof glue secreted by her reproductive glands and cemented to one side of the hair shaft, less than 6 mm from the scalp. The eggs hatch into nymphs after 7–10 days.
Clinical Features
Head Lice (Pediculosis Capitis)
- Symptoms: Intense scalp itching, worse at night or when the scalp sweats. Young children often seem unsettled, scratch their heads constantly and sleep poorly.
- Skin lesions: Red papules with an inflamed rim, weeping scratch marks and crusts, concentrated at the back of the head and behind the ears.
- Hair and nits: Nits are oval, about 0.8 mm long and opaque white or gray. They are firmly stuck to the hair and cannot be blown away or slid off by running a hand through the hair.
Common Complications
- Secondary impetiginization: Scratching breaks the skin and lets Staphylococcus aureus or Streptococcus pyogenes in, causing pustules, honey-colored crusts and oozing that mats the hair.
- Swollen lymph nodes: Tender, enlarged posterior cervical and occipital nodes in response to secondary infection.
Telling Nits Apart From Other Common Scalp Findings
| Viable Nits | Dandruff / Seborrhea | Hair Casts |
|---|---|---|
| Firmly cemented to one side of the hair shaft | Not attached; sits loose on the scalp or hair | Encircles the hair shaft and slides easily |
| Cannot be blown off or slid along by hand | Brushes off the hair very easily | Slides easily along the hair |
| Less than 6 mm from the scalp (live eggs) or farther out (hatched) | Lies on the scalp surface or falls loose | Scattered along the whole length of the hair |
| Oval, gray/brown, with an embryo and cap | Flat flakes of skin with irregular edges | Cylindrical sleeve around the hair |
| Not removed by washing with regular shampoo | Easily cleared or reduced by washing | Comes off after washing and gentle combing |
Our Diagnostic Process at Haute-Derma
History and Exposure: We ask about head-to-head contact at school or at home, and about sharing combs, helmets or pillows.
Wet Combing: The hair is dampened with water or conditioner, then combed from the scalp to the tips with a fine-toothed metal lice comb (teeth less than 0.2 mm apart) over white paper to look for moving lice.
Dermoscopy and Microscopy:
- Viable nit: An oval egg with a dark embryo inside and an intact cap (operculum).
- Empty nit: A hatched egg is just a translucent shell with a collapsed top. (Nits more than 1 cm from the scalp have usually hatched or are dead.)
Treatment and Outbreak Control at Haute-Derma
Topical Pediculicides
- Dimethicone 4%–100% (first-line):
- How it works: This silicone oil coats lice and eggs and blocks their breathing holes (spiracles), killing them physically by suffocation and disrupted water balance.
- Advantages: Resistance has essentially not been reported; it is very safe and rarely irritates the scalp.
- How to use: Apply evenly to dry hair from roots to tips, leave on for 8–15 minutes (or as directed for the specific strength), then comb out the lice and wash thoroughly.
- Permethrin 1% (lotion/creme rinse):
- An insecticide that acts on the louse nervous system. Apply to damp hair after shampooing (without conditioner), leave for 10 minutes, then rinse well.
- Note: Because permethrin resistance is increasing, the regimen always includes a second application 7–9 days later to kill newly hatched lice.
Mechanical Nit Removal: Wet-comb with a fine-toothed comb and conditioner every 3–4 days for 2 weeks to clear any remaining eggs and young lice.
Environmental Control and Preventing Spread
- Personal items: Soak combs and hair clips in hot water (above 60°C) for 10 minutes. Wash bedding, pillowcases, hats and clothing in hot water and tumble-dry on high heat.
- Items that can't be washed: Seal them in a tightly tied plastic bag for 2 weeks. Lice away from a host die within 48 hours without a blood meal, and any eggs that hatch will also die without blood.
- Checking the family: Check the scalp of every household member and treat anyone with signs of infestation at the same time.
