Scabies is a contagious skin condition caused by a microscopic mite, the Sarcoptes scabiei var. hominis, which is too small to be seen without magnification. This infestation is common worldwide and affects people of all ages and socioeconomic backgrounds; it is not an indicator of poor hygiene. Understanding how this condition spreads, particularly through common interactions like hugging, is important for managing public health concerns.
What Scabies Is and How It Affects Skin
The causative agent of scabies is a tiny, eight-legged mite. The female mite burrows into the stratum corneum, the outermost layer of the skin, where she lives for about four to six weeks. During this time, she deposits two to three eggs each day within the shallow, serpentine tunnels she creates.
The eggs hatch into larvae within three to four days and travel to the skin surface to mature. The intense itching associated with scabies is not caused by the burrowing itself but is an allergic reaction. This reaction is the body’s immune response to the mites’ proteins, saliva, and fecal matter left behind in the skin. Most people with classic scabies are infested with only about 10 to 15 adult mites at any given time.
Transmission Routes and Duration of Contact
Scabies transmission occurs almost exclusively through direct, prolonged skin-to-skin contact with an infested person. Since the mites cannot fly or jump, sustained physical proximity is required for them to crawl from one host to another. For a successful transfer in common scabies, this contact typically needs to last for a significant duration, generally estimated to be 10 to 20 minutes or longer.
Because extended contact is required, casual, brief interactions such as a quick hug, handshake, or high-five pose a very low risk for transmission. Transmission happens most frequently among household members, intimate partners, or in crowded settings like nursing homes or childcare facilities. Indirect spread through contaminated items like clothing or bedding is rare because the mites cannot survive long, typically only two to three days, away from a human host.
A more contagious form, known as crusted or Norwegian scabies, presents a different risk profile. People with crusted scabies have a compromised immune system, leading to an infestation of thousands or even millions of mites. In these cases, transmission can occur with brief skin contact or through contact with clothing, bedding, or furniture due to the massive number of mites being shed.
Identifying Scabies Symptoms
The most recognizable sign of a scabies infestation is severe and relentless itching, medically termed pruritus, which characteristically worsens at night. This nocturnal itching often interferes with sleep.
A rash that looks like tiny pimple-like bumps, hives, or small blisters often accompanies the itching. In some cases, a person may also see tiny, raised, wavy lines on the skin surface, which are the visible burrows created by the female mite. Common sites for these symptoms include:
- The webs of the fingers
- The insides of the wrists
- The elbows
- The waistline
- The armpits
- The genital area
Symptoms may take between three to six weeks to appear following a person’s first infestation, but the person is contagious during this symptom-free period.
Treatment and Home Prevention Strategies
Effective treatment for scabies requires a medical diagnosis and prescription medication, as over-the-counter products are not sufficient to eradicate the mites. Healthcare providers typically prescribe a topical cream or lotion, known as a scabicide, which must be applied to the entire body from the neck down and left on the skin for eight to 14 hours. Because the medication does not reliably kill all the eggs, a second application is usually required seven days later to eliminate newly hatched mites.
All close contacts and household members must be treated simultaneously, even if they show no symptoms, to prevent re-infestation. To eliminate mites from the environment, all clothing, bedding, and towels used by the infested person within three days prior to treatment must be washed in hot water, at least 122°F (50°C), and dried in a hot dryer. Non-washable items can be sealed in a plastic bag for at least three days, as the mites will die without a human host during that time.