Overview
Scabies is a contagious skin infestation caused by the microscopic mite Sarcoptes scabiei. The female mite burrows into the outer layer of the skin to lay eggs and complete its life cycle. The itching and rash associated with scabies are largely the result of the body’s allergic reaction to the mites, their eggs and their waste products rather than to mechanical damage.
Causes and life cycle
The parasite responsible for scabies is an ectoparasitic mite that lives on and within human skin. A fertilized female penetrates the stratum corneum and creates short, serpiginous tunnels where she lays her eggs. Eggs hatch into larvae and develop into adult mites on the skin surface. Mites are tiny and usually invisible to the naked eye; diagnosis typically relies on clinical features and tests rather than seeing the organism directly.
Symptoms and clinical features
Common signs include intense itching (often worse at night), small red bumps, and short linear burrows. Lesions frequently appear in characteristic sites such as the finger webs, wrists, elbows, armpits, waistline, buttocks, and genital area; in young children and infants, the face and scalp can also be involved. A severe and highly contagious form called crusted (or Norwegian) scabies can occur in people with weakened immune systems and is marked by thick crusts and very large numbers of mites.
Transmission and risk factors
Scabies spreads most often by prolonged direct skin-to-skin contact with an infested person. Close personal contact in families, child-care centers, group homes, prisons and other crowded settings facilitates transmission. It is possible to transmit scabies before symptoms develop, and household members and close contacts are typically treated at the same time to prevent reinfestation. Shared bedding, clothing or towels may carry mites for a short period and are often cleaned as part of control measures.
Diagnosis and treatment
Diagnosis is usually clinical, based on the appearance and distribution of lesions and a history of contact with an affected person. Dermatologists may confirm the diagnosis with methods such as dermatoscopy or microscopic examination of a skin scraping to find mites, eggs or fecal pellets. Treatment aims to kill the mites and relieve itching. Typical approaches include topical scabicides (for example, permethrin cream applied according to product guidance) and, in certain situations, oral ivermectin. All close contacts should be treated simultaneously. Itching and skin inflammation can persist for a few weeks after successful treatment because of persistent allergic reaction, even when mites are eliminated.
Prevention and public-health considerations
Prevention relies on identifying and treating cases promptly, treating close contacts, and implementing environmental measures such as laundering bedding and clothing in hot water or sealing unwashable items for several days. In institutional outbreaks, coordinated mass treatment and improved hygiene and living conditions are often necessary. Although scabies affects people globally across socioeconomic groups, overcrowding and limited access to water and healthcare increase transmission risk. For more information and guidance on management in different settings see official recommendations.