Scabies is a common, highly contagious skin condition resulting in relentless itching and an uncomfortable rash. This infestation can affect anyone and is a worldwide public health issue. Understanding how scabies is transmitted requires clarifying the nature of this unique infestation and the microscopic organism responsible.
What Exactly is Scabies?
Scabies is a parasitic infestation caused by the human itch mite, Sarcoptes scabiei variety hominis. These microscopic arachnids are obligate parasites that must live on a human host to survive and reproduce. The infestation begins when a female mite, measuring less than half a millimeter, penetrates the outermost layer of the skin (the stratum corneum). Once burrowed, the female mite creates shallow tunnels where she deposits eggs and fecal pellets called scybala. The intense itching and rash are caused by the body’s allergic reaction to the mites, their eggs, and their waste products.
How Scabies Spreads Through Close Contact
Scabies is primarily transmitted through prolonged, direct skin-to-skin contact with an infested person. Transmission typically requires contact lasting at least 10 to 15 minutes, allowing the mite time to transfer hosts. Because sexual intercourse involves sustained, close physical contact, scabies is often passed between partners during sexual activity. However, scabies is not classified exclusively as a sexually transmitted disease (STD) because it is easily transmitted through non-sexual means.
The key differentiator is that transmission does not require the exchange of bodily fluids, unlike traditional STDs. Non-sexual routes include extended physical interaction, such as a parent holding an infant or close contact within a household. Scabies spreads rapidly in crowded settings like nursing homes, extended-care facilities, and prisons. While uncommon in classic scabies, mites can survive for 48 to 72 hours away from a human host, meaning transmission through contaminated objects like clothing or bedding is possible.
Identifying and Confirming Scabies
The defining symptom of scabies is severe itching, which characteristically worsens at night. This nocturnal itching is often intense enough to disturb sleep, sometimes leading to secondary skin infections from excessive scratching. The infestation also presents as a pimple-like rash, which may include tiny red bumps or blisters. For a person who has never had scabies, symptoms can take four to six weeks to appear following the initial infestation.
The physical signs of scabies are typically found in specific areas where the mites prefer to burrow. These areas include:
- The webs between the fingers.
- The bends of the wrists, elbows, and knees.
- Areas along the waistline.
A physician can sometimes identify the mite’s tunneling, which appears as tiny, grayish-white, wavy lines on the skin surface. Definitive diagnosis requires a medical professional to perform a skin scraping, examining a small sample of skin under a microscope. This confirms the diagnosis by identifying the presence of the mite, eggs, or fecal matter.
Effective Treatment and Eradication
Treating a scabies infestation requires a dual approach targeting both the infested individual and their immediate environment. Medical treatment involves prescription medications called scabicides, which kill the mites and their eggs. The most common first-line treatment is Permethrin 5% cream, a topical medication applied to the entire body from the neck down and washed off after eight to 14 hours. Oral medication, such as Ivermectin, may also be prescribed for widespread or persistent cases.
All household members and close physical contacts must be treated simultaneously, even if they are not yet showing symptoms. This prevents the cycle of re-infestation from asymptomatic individuals. Environmental control focuses on items that have been in prolonged contact with the infested person’s skin within the last three days. Bedding, clothing, and towels should be washed using hot water and dried on a hot cycle.