Who besides lice can live on the head? - briefly
Various organisms can inhabit the scalp besides lice, including mites, fungi, and bacteria. Mites cause dandruff, fungi cause ringworm, and bacteria may lead to folliculitis.
Who besides lice can live on the head? - in detail
The scalp serves as a habitat for a variety of organisms beyond the well‑known head louse. These inhabitants fall into several categories, each occupying distinct ecological niches.
• Acari mites – primarily the Demodex folliculorum and Demodex brevis species. They reside within hair follicles and sebaceous glands, feeding on sebum and cellular debris. Population density increases with age and can contribute to conditions such as rosacea or blepharitis.
• Fungal agents – most commonly Malassezia spp., which thrive on the lipid‑rich environment of the scalp. Overgrowth manifests as dandruff or seborrheic dermatitis, characterized by flaking and erythema.
• Bacterial flora – includes Staphylococcus epidermidis, Propionibacterium acnes, and Corynebacterium spp. These microorganisms form a stable microbiome that protects against pathogenic invasion but may become opportunistic under altered skin conditions.
• Other arthropods – rare occurrences of flea or tick attachment are documented, usually secondary to contact with infested animals. These ectoparasites may cause localized irritation and secondary infection.
• Nematodes – the microscopic worm Trichinella spiralis has been reported in isolated cases of scalp infestation, typically linked to ingestion of contaminated meat rather than direct colonization.
• Scalp‑associated protozoa – Acanthamoeba spp. can inhabit the moist surface of the scalp, especially in individuals with compromised immune systems, leading to inflammatory lesions.
The coexistence of these organisms reflects the scalp’s warm, humid, and nutrient‑rich conditions. Management of undesirable colonization involves targeted hygiene practices, appropriate topical or systemic therapies, and, when necessary, professional medical evaluation. «Effective treatment requires identification of the specific organism and selection of an agent with proven activity against it».