Intestinal parasites that may infect children come in two varieties: protozoa and helminthes. Protozoa are single-celled worms. They are able to multiply inside the human body and can be a major cause of infection. Helminthes are multi-celled organisms, the most common forms being pinworms and tapeworms.

Head lice is common in schools and other environments with large numbers of people. Lice can spread by head-to-head contact, but you can also catch it through indirect contact, like using someone else's brush, borrowing someone's hat or even cuddling with an infected person's stuffed animals.

Whether they are pinworms, tapeworms, or microscopic protozoa like Giardia lamblia or amoebas, intestinal parasites are never beneficial. They attach to the lining of your bowels, typically living off the food you eat and damaging your intestinal cells.

Scabies is a common contagious skin condition caused by Sarcoptes scabiei, a microscopic mite, that burrows into the upper skin layer to drop its eggs. On human skin, scabies looks like a rash or blisters. It can also appear as pimples or small bumps, reports the American Academy of Family Physicians.

Lice, or pediculus humanus capitis, are wingless, parasitic insects that annually affect approximately 6 to 12 million U.S. children ages 3 to 11. Lice transmission occurs from direct contact with inanimate objects, such as a comb, brush, hat or scarf.

Intestinal worms grow in children who have ingested larva eggs, typically from exposure to soil or surfaces contaminated with human feces. Three common types of intestinal worm affecting children in the United States are pinworms, tapeworms and roundworms. Together, they make up a group of parasites called helminths.

Intestinal parasites such as parasitic worms infect more than one-fourth of the world's population, according to the World Health Organization. These infections result in disease, disability and death.

Ringworm is a fungal infection that can affect skin anywhere on your body. Jock itch and athlete's foot are common names for this type of infection. Warm, moist environments like steam rooms, saunas, pools and gyms are a perfect breeding ground for ringworm to thrive.

Ringworm thrives in dust, pet dander and moist, dark places in the home. On occasion, it may be necessary to rid the home of ringworm, especially if a household member or pet has a ringworm infection. Ringworm is a fungus that causes skin infections, and ringworm is contagious.

Tapeworms enter the human body through consumption of contaminated food or improper food handling. The most common type of tapeworms are found in beef (Taenia saginata) and pork (Taenia solium). The medical term for tapeworm infection is Taeniasis.

Many food-safety resources, including the USDA, recommend against consuming unbaked cookie dough because of the risk of illness. Eating raw cookie dough can result in gastrointestinal illness that may even lead to hospitalization in extreme cases.

Roundworms include more than 15,000 known species and up to half a million unknown species. Most do not cause disease, but several species can infect humans, causing symptoms that range from mild to severe. Although serious roundworm infections are uncommon in the U.S.