Mange is a general term describing a parasitic skin condition caused by mites that live on or under the skin of animals. When a similar infestation occurs in humans, the condition is specifically named scabies, caused by the microscopic mite Sarcoptes scabiei var. hominis. While animal mites can briefly affect human skin, they cannot establish a sustained infestation. The effect on humans is typically limited to a temporary, self-limiting irritation.
The Direct Connection: Mange vs. Scabies
The distinction between mange and human scabies lies in the specific variety of mite involved and its ability to reproduce on a host. Mange in animals, such as dogs, is frequently caused by host-specific varieties like Sarcoptes scabiei var. canis or Demodex mites. These animal mites are adapted to their primary host and cannot complete their reproductive cycle on human skin.
If a person contacts an infected animal, the animal mites may burrow into the skin, causing a transient irritation. This irritation is temporary because the mites quickly die off without reproducing, resolving spontaneously once contact with the infected animal is removed. True human scabies is caused exclusively by Sarcoptes scabiei var. hominis, a variety that is an obligate parasite of humans.
This human-specific mite burrows into the outermost layer of the epidermis, the stratum corneum, where the female lays its eggs. The female mite can lay two to three eggs daily, completing its life cycle (egg, larva, and nymph stages) entirely within a human host over 10 to 17 days. This successful reproduction maintains a persistent infestation in humans, unlike the short-lived irritation caused by animal mites.
How Human Infestation Spreads
Transmission of human scabies primarily requires prolonged, direct, skin-to-skin contact with an infested person. This extended contact allows enough time for the mites to crawl from one person to another. Brief interactions, such as a quick handshake or hug, do not provide the necessary opportunity for transfer.
Transmission often occurs during intimate physical contact, such as sexual contact, or among family members living in the same household. The mites also spread readily in crowded environments where close personal contact is frequent, including nursing homes, extended care facilities, and childcare centers.
Indirect transmission through shared objects is less common but possible. This typically involves sharing items like clothing, towels, or bedding recently used by an infested person. The risk of indirect spread is significantly higher in cases of crusted (Norwegian) scabies, where the person harbors a massive number of mites, making the environment more contaminated. Scabies mites do not survive more than two to three days away from human skin.
Recognizing the Signs of Infestation
The most common sign of human scabies is intense itching, which worsens at night or after a hot bath. This severe itching is an allergic reaction to the presence of the mites, their eggs, and their fecal matter within the skin. Because symptoms result from an allergic response, the onset of itching can be delayed by two to six weeks after the initial infestation in a person who has never had scabies.
The physical appearance typically involves a pimple-like skin rash consisting of small, red bumps or vesicles. The most telling sign, though often difficult to see, is the presence of mite burrows, which appear as tiny, short, wavy, raised lines on the skin surface. These burrows are created by the female mite tunneling just beneath the skin to lay her eggs.
Infestation sites tend to concentrate where the skin is thin or folded. Common locations include the webbing between the fingers, the skin folds around the wrists, elbows, and knees, and the waistline, belt line, and genitals. In infants and very young children, the rash may be more widespread, sometimes involving the palms of the hands, the soles of the feet, and the scalp.
Treatment and Environmental Eradication
Treatment for human scabies requires prescription-strength medications known as scabicides, which kill the mites and their eggs. The most common first-line treatment is a topical application, such as 5% permethrin cream, applied to the entire body from the neck down and left on for 8 to 14 hours before washing off. Oral medications, such as Ivermectin, may be prescribed, particularly for individuals who cannot use topical treatments or those with crusted scabies.
To prevent re-infestation, it is necessary to treat all close personal contacts and household members simultaneously, even if they are not showing symptoms. A second application of the scabicide is often recommended one week after the first treatment to kill any newly hatched mites. The persistent itching after successful treatment, which can last up to four weeks, is a sign of the continuing allergic reaction and does not indicate treatment failure.
Environmental control measures are also necessary for successful eradication. All clothing, bedding, and towels used by the infested person during the three days before treatment must be washed in hot water and dried on a high-heat cycle. Temperatures exceeding 50 degrees Celsius for at least 10 minutes are sufficient to kill the mites and their eggs. Items that cannot be washed, such as stuffed animals or unwashable shoes, should be sealed in a plastic bag for a minimum of 72 hours to ensure any remaining mites die.