Scabies is a skin infestation caused by a tiny, eight-legged mite known as Sarcoptes scabiei. These microscopic mites burrow into the uppermost layer of human skin, where they live, feed, and deposit their eggs. The body’s reaction to these mites and their byproducts causes the characteristic symptoms. Scabies is highly contagious and typically spreads through prolonged skin-to-skin contact.
The Distinctive Rash and Burrows
Scabies often begins with a rash, appearing as small, red bumps resembling pimples, hives, or tiny bites. These bumps may also present as fluid-filled blisters or scaly patches, varying in color from red, brown, or gray depending on skin tone. Sometimes, the rash forms a linear pattern across the skin.
A tell-tale sign of a scabies infestation is the presence of burrow marks. These are created as the female mites tunnel just beneath the skin’s surface to lay their eggs. These burrows typically appear as tiny, raised, irregular lines, often described as wavy or thread-like, measuring between 1 millimeter and 1 centimeter in length. They can be grayish-white or skin-colored, and sometimes a tiny black speck, representing the mite, can be seen at one end. These burrows are a direct indication of mite activity and differentiate scabies from many other common skin conditions.
The Intense Itch
Intense and persistent itching is the most prominent symptom of scabies. This itching is often severe and can be particularly disruptive at night, frequently worsening after a hot bath or shower.
The severity of the itch can lead to continuous scratching, which in turn can cause secondary effects on the skin. Frequent scratching may create open sores or painful bumps, increasing the risk of secondary bacterial infections like impetigo. These secondary infections can sometimes lead to more serious complications if left unaddressed.
Where Scabies Commonly Appears
Scabies mites prefer specific body areas, making symptom location a diagnostic clue. In adults and older children, the rash and itching are most commonly found in skin folds and softer areas. This includes the webs of the fingers, the wrists, elbows, and armpits.
Other frequent sites of infestation include the waistline, buttocks, and the skin around the nipples and genitals. Areas around the belly button and skin covered by jewelry, such as rings or watchbands, are also common locations. In infants and very young children, scabies can present more broadly, often appearing on the scalp, face, neck, palms, and soles of the feet.
Variations in Appearance
Scabies appearance can vary depending on individual circumstances. A more severe form, known as crusted scabies or Norwegian scabies, typically affects individuals with weakened immune systems, the elderly, or those who cannot scratch effectively. In crusted scabies, the skin develops thick, scaly crusts that may appear gray and crumble easily.
This severe variant involves a significantly higher number of mites, sometimes millions, compared to the typical 10 to 15 mites seen in classic scabies. Despite the extensive infestation, the intense itching may be minimal or absent in crusted scabies. In infants, the rash can be widespread, potentially covering the entire body, and may feature fluid-filled bumps on the palms and soles, making diagnosis more challenging in these groups.