5 Parasites That Breed On and In Your Skin

Lice are a real pest. If you're a parent of a school-aged child, you probably already know that.

There are three broad categories of lice that plague humans — head, body and pubic lice. Lice feed by biting and drinking the blood of their hosts. Body lice don't live on the skin itself — they inhabit clothing and only move to the skin to feed. But head and pubic lice live directly on the skin.

The louse can't fly or jump — it can only crawl. When a female louse lays eggs, it does so at the base of a shaft of hair. The eggs — or nits — are oval and usually white, yellow or a color similar to that of the hair to which they're attached. Larvae hatch from the eggs after a few days. A little more than a week later, the larvae have matured into adults capable of reproducing.

There are several treatments for lice. Most of these treatments are in the form of medicated shampoos. Human lice are transferred by close contact with infected humans — in other words, you won't catch lice from animals.

The chigoe flea (Tunga penetrans) is known by many names, including the jigger flea and the sand flea. Regardless of what you call it, the parasite latches onto its host's skin to feed — typically the toes, sole and heel of the foot. Then the flea breathes, defecates and lays eggs through its hind legs — the only part of the flea that remains exposed to air once it latches on.

Female jigger fleas penetrate into the skin of the host and lay hundreds of eggs. This egg-laying period can last up to three weeks. Then, the female dies and eventually falls off the host. Once her eggs hatch, the fleas bite their host and the cycle continues. As these new fleas develop, area around them swells and becomes painful and itchy. The infection is called tungiasis.

The chigoe flea is found mainly in South American and African regions. It normally attacks between the toes of hosts but can latch onto other parts of the body as well. The fleas can also cause necrosis — tissue death — that often must be removed with surgical tools.

Another microscopic parasite that breeds under our skin is the scabies (Sarcoptes scabiei). These tiny mites transfer from person to person through skin contact and cause an intensely itchy skin rash where the scabies burrow. Scabies are especially troublesome within a household or any community with a dense population. Prisons, nursing homes and childcare facilities can be vulnerable to outbreaks. What's worse, the first time someone is infected, they may have no symptoms for up to two months, but will still be contagious during that time.

The scabies mite burrows into the skin and lives out its life cycle there, including laying eggs. One variety called Norwegian, or crusted, scabies is particularly severe. It is characterized by thick crusts of skin with large numbers of scabies mites and eggs. It mostly occurs in people who are immunocompromised and the elderly. Crusted scabies is very contagious and can spread by direct contact and through contaminated clothes, bedding and furniture.

Scabies is relatively easy to treat with scabicides — prescriptions that kill the mites and eggs. The most common versions come in the form of a lotion or cream.

File this one under "I hope this never happens to me." The Loa loa worm is a several-centimeter-long nematode that infects millions in Western and Central Africa via deerfly (Chrysops) bites. It can stay in a host human's body undetected for years. Some people may have itchy swelling that comes and goes on the body, most commonly near the joints. Less common symptoms include itching all over the body, muscle pain, joint pain and fatigue.

But one day the infected person may feel something strange in their eye and look in the mirror only to see — gasp — a tiny worm on their eyeball. That's how the Loa loa worm got its nickname, "African eye worm." It's endemic to countries like Cameroon and Sudan.

Once it's been detected, the infection (loiasis) can be treated with the drug diethylcarbamazine. That will kill early stages of the parasite in the bloodstream. But adult worms in the eye requires surgical removal.

The human botfly (Dermatobia hominis) is found in tropical areas of Central and South America and the Caribbean. It's one of several flies that can cause tissue infection by a fly larvae (maggots). The fly itself doesn't harbor any diseases, but the larvae infest the skin of mammals — preferably humans — and lives out the larval stage in the subcutaneous layer. It wreaks havoc there creating painful pustules. This type of infestation is called myiasis.

Botflies depend other feeding insects to get their work done. They capture other bloodsuckers and deposit their mature eggs on them — usually mosquitoes or ticks. When these guys go in for blood, the eggs react and hatch. The larvae then enter the skin where they can stay for up to 10 weeks, breathing through an airhole.

Human botfly larvae can cause a raised lesion in the skin that becomes hard and painful. Sometimes people infected can even feel the larvae moving. That's why treatment often includes using petroleum jelly to block the airhole, which causes the maggot to pop out, though other times it must be surgically removed.