Scabies is caused by a mite (a tiny insect-like organism) that's hardly visible without a microscope. The mite is disc-shaped, pearly-white in colour, with 4 pairs of brown legs, and reaches an adult size that is less then 0.5 mm.
Scabies mites can infest warm and moist folds of skin, such as armpits, buttocks, or groin. They can be found behind the knees, on the inside of elbows and wrists, or between fingers. Scabies usually isn't seen on the scalp or on the palms of hands or the soles of feet. It is possible, however, for young children or people who harbour very large numbers of mites to be susceptible in those areas. Seniors might also find mites at the hairline, neck, temple, and forehead regions.
Scabies is quite a common condition, affecting 300 million people worldwide.