Dear doctor: My wife and I had to go back to our offices, so our 4 year old son is back in daycare. About six weeks later, he got an itchy rash that drove him crazy. Her pediatrician says it’s scabies. What is that? She says it’s likely he got it in daycare, and we’re worried it will happen again.

Dear reader: The word “scabies” comes from the name of a microscopic mite known as Sarcoptes scabiei var. hominis – the human itch mite.

Scabies are tiny insect-like organisms – the size of a pinpoint – that are linked to ticks. They are extremely contagious and are spread through direct and prolonged human contact. You won’t get itch from a quick hug or handshake. However, in situations such as a daycare center, where children spend a lot of time together in tight spaces, play physically, and often share common toys, pillows, and blankets, an infestation can spread quickly.

The impregnated female mites burrow under the top layers of the skin, where they create tunnels and lay two to three eggs per day. Once hatched, the mite larvae return to the surface of the skin. There they build what are called moulting pockets, where they mature. The new adults will then migrate either to other parts of the body or to the skin of another person.

The itchiness associated with scabies comes from the body’s allergic reaction to dust mites, their eggs, and wastes. In a person who has never had scabies, it may take four to eight weeks for an allergic reaction to develop. Once it starts, it’s an often exasperating itch that becomes especially persistent at night.

Along with the itchiness, the symptoms of scabies include a rash like the one your son had. It may look like beehives; clusters of small bumps, knots or pimples; or patches of scaly skin. In children, mites are most commonly found on the face, neck, and scalp, and they can also be present in the palms of the hands, fingers, and soles of the feet. Diagnosis is based on the distinctive appearance and distribution of the rash and the presence of burrows.

Scratching can lead to open sores, which are susceptible to secondary infection. Treatment with prescription drugs known as scabicides is effective. Over-the-counter products have not been tested or approved for the treatment of scabies. Antihistamines, anti-itch lotions, and steroid creams may be prescribed to relieve the itchiness.

Because scabies are so contagious, it’s important for anyone affected to alert those around them. It is recommended that entire families or contact groups, such as children, staff and parents involved in your daycare, undergo treatment at the same time.

Bedding, clothing and other textiles should also be treated. Without a host, scabies cannot survive beyond 72 hours, so contaminated items should be fully sealed in plastic bags for at least that long. It is also effective to wash them in very hot water and dry them in a very hot dryer. While it is possible for the problem to reoccur, a thorough and vigilant response should eradicate the problem.