You're lying in bed at night when you suddenly feel an itch on your leg. Without giving it much thought, you reach down and scratch. No big deal, right? But in the morning, your small itchy spot has turned into an angry-looking rash, and it's even itchier. Is it just some weird allergic reaction, or could it have come from a parasite?
Skin parasites are generally small insects, worms or other bugs that feed on blood or other bodily material. These creepy-crawlies usually fall into one of two categories: external or internal. External parasites tend not to hang around for very long. Most of them either jump on and off, or they leave once they've had their fill. Other parasites try to stick around for longer periods of time. Internal skin parasites burrow under the skin to feed, lay their eggs and make a temporary home for themselves.
Some skin parasites spread between people or other animals, but you can also pick them up from just being in a particular environment. While getting a skin parasite is often more of a nasty nuisance than anything else, a few of these critters can cause some real problems. But the good news is that you can generally prevent a skin parasite infestation by avoiding certain areas or activities, using appropriate insecticides and wearing protective clothing.
So how can you tell whether that itchy rash was caused by a skin parasite? There are a few general symptoms. First, you have an itchy, crawling feeling on or just under your skin. You might also experience biting, stinging or other pain associated with your rash. The rash might be streaky or could consist of pustules that look a little bit like acne. Also, with many skin parasites, basic over-the-counter treatments for itching don't take care of the problem. If you don't think that you've come in contact with anything else that might cause a rash, it could be time to get to a doctor so you can get the proper treatment.
In this article, we'll learn all about some of the most common skin parasites and how our perceptions of them have changed over the years. Let's start by looking at a very common external skin parasite that afflicts both man and his best friend -- the flea.
If you have a cat or dog, and they spend a lot of time outside, you might have some experience with fleas. Fleas are extremely tiny wingless insects that can jump huge distances and have mouths designed to bite and draw blood [source: Bohart Museum of Entomology]. Fleas reproduce quickly and can have a life cycle of just a few weeks, but they may live longer depending on the conditions.
Typically, fleas attack mammals, including humans, and birds. If you get bitten by one, it's probably because your cat or dog has brought them into the house. You'll notice your pet scratching or chewing its fur, and may see "flea dirt," or tiny black specks of flea feces, in its fur. Fleas are just as happy to feed on your blood as your pet's, although they're more likely to stay for a longer time on your pet's body because they can hide in its fur.
Flea bites usually appear in clusters or lines on the skin and each looks like a dark-reddish bump ringed in pink. Just the bite could be enough to make you feel itchy. However, many people (and animals) are also allergic to flea saliva. This means that the bites cause an allergic reaction and spread into a rash. Fleas can also carry diseases such as bubonic plague, or the Black Death. Treating the itch is the simplest part of dealing with a flea infestation -- over-the-counter hydrocortisone creams or calamine lotion can help.
But unless you treat your pet and your house, you'll keep getting bitten. Fleas lay eggs in hidden places like carpets, and their larvae hatch and grow into adult fleas within a few days. Their hard bodies make it difficult to kill them directly? -- they are resistant to the scratching and can't be crushed or pinched. Usually treatment means using insecticides, but there are natural ways to eliminate fleas as well, such as dried pennyroyal and cedar oil. No matter what you use, though, it can take awhile to be completely rid of fleas. To prevent them, you can keep your pet on a flea treatment regimen, especially in the summer.
In the next section, we'll look at another skin parasite that is even clingier than the flea -- the tick.
Ticks are small arachnids (in the same family as spiders) who feed on the same types of animals as fleas do -- mammals and birds [source: Illinois Department of Public Health]. Most species are smaller than the head of a match, with round bodies and six or eight legs. Their sharp mandibles pierce your skin, and then a feeding tube called a hypostome is inserted and the meal begins. Unlike fleas, ticks' bodies expand as they feed, so they don't stay tiny. Once a tick is attached, it stays until it's completely full of blood. This can take a couple of days.
Pets and people pick up ticks when they're out in the woods, because ticks like hanging out in meadows, bushes and tall grasses. They also live near water sources so they can glom on to mammals that come to drink. Their bite is usually painless, so you probably won't know that you've picked up a tick until you spot it on your body [source: Illinois Department of Public Health]. If your pet has gotten a tick, the bug might move to you when it's gotten its fill or if your pet manages to scratch it off.
It's important to remove a tick as soon as you spot it, because they can spread serious diseases (see the sidebar on this page) [source: MedlinePlus]. There are lots of old wives' tales for the best way to remove a tick, including rubbing it with petroleum jelly or holding a match to its body. These can actually make the problem worse, because they will make the tick inject more of its saliva into your skin. Instead, grab the tick's body as close to the skin as possible with a pair of tweezers and pull firmly.
Wash the bite area with soap and water, and treat any itchiness with over-the-counter medications [source: Illinois Department of Public Health]. If you can't remove the tick, it's time to see a doctor. You should also see a doctor if you have a round rash around the bite or start to feel weak or nauseated after removing it. To prevent getting ticks in the first place, wear long pants and long-sleeved clothing in heavily forested areas and use tick repellant. Also, perform a tick check when you come inside, and immediately take a shower.
Ready to learn more about external skin parasites? Next up, the bane of the public school system: lice.
If you ever had head lice as a child, don't feel too bad -- it's pretty common because these tiny (sesame seed-sized) wingless insects spread so easily in groups of people living or staying together in close quarters [source: U.S. National Library of Medicine]. Lice eat not only blood, but also dead skin and body secretions. There are three different types of lice that infect humans: head lice, body lice and pubic lice (or crabs). Body lice and head lice have similar appearances, while pubic lice actually do have a crab-like appearance [source: CDC].
Lice attach themselves to their host's hair and affix their eggs to the hair with saliva, but their bites don't usually hurt or cause bumps. Lice infestations are called pediculosis [source: CDC]. Head lice spread through direct contact or sharing hairbrushes with an infected person. Body lice (which live in clothing) spread through shared clothing or towels. While pubic lice are often spread through sexual contact, they can also be transferred through shared clothing.
Diagnosing any type of lice requires careful examination of the hair, usually by using a special fine-toothed louse comb. Once the eggs hatch, it is easy to spot the empty shells (or nits) as they are white or whitish-yellow and are hard to remove from the hair. You may also see tiny black louse feces in the hair or on pillows. As with fleas and ticks, itching is caused by sensitivity to the bug's saliva, and it can be bad enough to keep you awake at night.
It can take awhile to be completely rid of the lice and nits. Usually you have to combine several different types of treatment options and repeat them two or three times. These include treating the scalp with a chemical pediculide such as pyrethrin. Combing through conditioner or oil-coated hair and flushing any lice or eggs caught clinging to the comb is also helpful. Some people have used things like gasoline, kerosene vinegar or hair bleach to get rid of lice, but these home remedies aren't effective (and, in the case of gasoline or kerosene, can be dangerous). You can also treat body and pubic lice with pyrethrin or other chemical insecticides. All clothes and linens must be washed in hot water.
Can you fill in the blank in this phrase: "Good night, sleep tight, don't let the ____ bite"? Learn about another external skin parasite next.
There are lots of different types of bedbug, another small, flat oval insect that feeds on mammal blood. Adult bedbugs are about the size of an apple seed, less than a quarter of an inch (6.35 millimeters) long [source: Pollack]. They're drawn to body heat and carbon dioxide and usually crawl to or drop down on their victims. To feed, they pierce the skin with two tubes -- one injects saliva (which contains both an anticoagulant and a numbing agent), while the other is for feeding. A bedbug bite doesn't hurt right away, and the bedbug quickly retreats when it's done. Once again, it's the saliva that causes an itchy allergic reaction and leaves you with raised welts that are often in a cluster or row on the skin.
True to their name, bedbugs prefer to hide in mattresses and other types of furniture. They are so flat that they can squeeze into very tiny openings, making them difficult to spot. They're also mostly nocturnal, which is why you're at risk for being bitten when you're in bed. Extreme scratching of the bites, as with other skin parasite bites, can lead to infection. Bedbugs can also carry diseases, but research shows that it's unlikely that they can spread them to their hosts. Instead, infestations typically just result in itching, discomfort and sleeplessness.
Due to increased travel and restricted pesticide usage, bedbug infestations are on the rise in industrialized countries where they had previously disappeared [source: Stoppler]. People often bring them to hotels in their suitcases or take them home the same way. In addition to seeing a bedbug or noticing the bites, you might spot an infestation by the droppings, which are tiny, black spots on a mattress or other bedding. You can treat the itching with over-the-counter anti-itch creams like hydrocortisone, but the only way to get rid of bed bugs is to use insecticides and steam-clean with temperatures reaching at least 120 degrees Fahrenheit (49 degrees Celsius).
If these external skin parasites weren't gross enough, next we'll look at internal, or burrowing, parasites. Meet the scabies mite.
A scabies mite is round, flat miniscule arthropod around 0.02 inches (0.4 millimeters) long (source: American Academy of Dermatology]. It looks a little bit like a turtle and has spines on its body. Scabies mites cause an infection known as scabies or mange in humans, dogs and cats, as well as other animals like horses, goats and sheep. The mites feed on skin cells and burrow irregular tracks just under the skin to feed and lay eggs. Their bites look like acne bumps. Both their presence and the burrowing cause the skin to react, creating intense itching. This leaves a person who has them with a scaly, flaking rash and thickened skin.
Typically the burrows start at the hands or feet, but they can spread quickly. A female scabies mite lays a few eggs a day, which hatch within the skin into larvae. The larvae also burrow and grow quickly into nymphs, then into adult mites, which mate. Adult mites can live for a few months, and the entire life cycle can essentially take place under the skin. Scabies mites are spread through contact with an infected person or animal as well as clothes, furniture and towels.
Because they're so tiny, it can be difficult to spot a single mite. The infection is usually diagnosed by the tracks left by the burrows, but scratching can also hide the tracks. To make them appear, you can rub the itchy area with ink and then wipe it with alcohol -- the tracks will appear. Doctors also diagnose scabies by looking at skin scrapings under a microscope. Animals with mange will often scratch themselves to the point of losing fur and getting open sores.
While the mites themselves don't spread disease, intense itching can lead to severe skin infections if left untreated. People with compromised immunity and the elderly can get a particularly painful and itchy type called crusted scabies. Treatment includes rubbing on an insecticide like permethrin or taking ivermectin, an oral antiparasitic. As with other skin parasites, treating the environment is essential -- everything should be washed in hot water and disinfected to prevent a re-infestation.
Not all fleas are created equal. In the next section, we'll look a type of flea called the chigoe.
While the parasites we've looked at so far are found all over the world, the chigoe flea, or jigger, lives mostly in Central and South America. It lives on the ground and feeds on humans and other mammals, mostly attacking the feet. The chigoe is different from other fleas in that it burrows under the skin to feed on blood and lay eggs. Unlike the scabies mite, it doesn't go completely under the skin. Instead, the chigoe digs a hole and inserts its head under the skin. Its respiratory organs and back legs stay outside the body so it can breathe while feeding. The chigoe also lays its eggs through the opening, which fall to the ground. Soon afterwards, it dies, but the eggs hatch into adults within a couple of days.
A chigoe bite looks like a small red dot with a black center -- the rest of the chigoe's body -- surrounded by a ring of white. A chigoe flea infection is known as tungiasis [source: Collins]. It causes skin inflammation, itching and pain. Even once the chigoe dies and falls off, the open lesion left behind is prone to infection and abscesses. Multiple chigoe bites, which are common among people who become infected, can lead to more severe conditions like gangrene and blood infections.
Because chigoes are partially visible on the skin, they're usually easy to diagnose. They can be removed with tweezers (with great care to avoid leaving the head under the skin) or suffocated and killed on the skin's surface with oil or petroleum jelly. Doctors often prescribe antibiotics to treat the infections. One of the most effective ways to ward off chigoes is to wear closed-toed shoes, but pesticides are also used.
In the next section, we'll look at an internal parasite that gets others to do its dirty work: the botfly.
The human botfly is a small, hairy fly found in Central and South America. Unique among skin parasites, the botfly itself doesn't actually burrow under the skin. Instead, it lays its eggs on mosquitoes, ticks or other flies. When a person is bitten by one of these insects, the eggs are triggered to hatch into maggots by a human's body heat [source: U.S. Army Center for Health Promotion and Preventative Medicine].
Botfly maggots burrow just under the skin and leave a hole through which to breathe while they feed off blood and tissue. The burrows look like large white boils, which swell under the skin and cause intense pain. Maggots also secrete a sort of antibiotic to ward off infection while they feed. As the maggot grows, it swells under the skin and causes intense pain. Victims may also feel it biting and wriggling around as it feeds. If not removed or otherwise disturbed, the maggot will drop out of its hole after six to eight weeks so it can pupate.
Because the maggots hook into the skin inside their burrow, they are difficult to remove. One method involves placing raw meat over the hole. When the maggot is unable to breathe, it burrows out into the meat. Other suggestions include covering the hole with glue, tape or petroleum jelly to suffocate the maggot. Trying to simply pull it out is usually unsuccessful because it may burst. Pieces can be left behind in the hole and cause an infection. Because of this, botfly maggots are best removed via surgery by a doctor. In the past, physicians have removed them from people's genitalia, arms, legs, chests, eyes and scalps.
Botflies can cause an infection or tissue damage depending on where the maggot burrows, but typically only a scar is left behind after the maggot's removal. The best way to prevent a botfly maggot infestation is to avoid being bitten by one of the adult fly's hosts. You should wear protective clothing and repellant when outdoors in areas where you're likely to get bitten.
We've looked at all manner of insects, from flea to flies, in the realm of skin parasites. Now, for something completely different: worms.
There are several different species of parasitic worms that become a problem when ingested, but worms that burrow into your skin are a rarer breed. These include a few types of the tiny, thread-like filarial worm, which can infect the body cavities, lymph system, eyes, or the fat layer just under your skin's surface. The latter two types cause an infectious disease called subcutaneous filariasis [source: DPDx]. These worms include the Loa loa (African eye worm), Onchocera volvulus and the guinea worm. They are found mostly along bodies of water in tropical areas of Africa, South America and Southeast Asia.
You can catch subcutaneous filariasis if you are bitten by a mosquito or fly infected with larvae. The filarial worm completes its entire life cycle in its human host. Once the larvae are injected by an infected bug, they grow into adult worms and reproduce, creating microfilariae. These juvenile worms' location just under the skin makes them ripe for being ingested by feeding mosquitoes and the cycle begins anew. People infected with filarial worms may have them for years, and adult worms can live for more than a decade. If the infection is to the eye, it is called onchocerciasis, or river blindness [source: DPDx]. This is the second-leading infectious cause of blindness in the world.
A diagnosis is difficult because the symptoms look like those associated with many other types of infections, and sometimes symptoms don't appear for years. Victims have an itchy rash and open sores, along with inflammation and pain. These symptoms can progress to a fever, body aches and headaches. Dying worms and bacteria can also cause secondary skin infections. There may be changes in skin color, or the worms can be seen crawling under the skin or the eye. The only way to diagnose for certain is to look for the microfilariae in the blood, which has to be drawn at night when the worms are most active.
According to the World Health Organization, filariasis is a potentially eradicable disease. To treat it, patients must take a drug called ivermectin to kill the microfilaria. However, as with other mosquito-borne skin parasites, avoiding getting bitten is the best way to keep from being infected. Use mosquito nets, avoid being in jungle areas at night, wear long sleeves and pants, and use insect repellent.
In the next section, we'll look at a worm that isn't a worm at all as well as a potentially new skin parasite.
Ringworm and Morgellons
You may be wondering why ringworm hasn't come up yet. That's because despite its name, ringworm is actually a fungus that lives in damp, warm places. The same fungus also causes athlete's foot and jock itch -- it just depends on where you're infected. The fungus feeds on dead skin tissue, and it causes a red ring of itchy, scaly skin that spreads outwards. If your infection is in the hair or your pet is infected, ringworm can cause bald patches. A nail infection will change the nails' color and might cause them to fall off.
Typically people catch ringworm from their pets or from other people through sharing clothing or grooming items like combs. You can treat mild infections with over-the-counter anti-fungal creams or powders that contain miconazole or clotrimazole, but you'll need to get a special fungicide from the vet for your pet. You should also use fungicidal soap on your clothing and on yourself. More serious cases may require a prescription. Doctors can diagnose ringworm typically by the rash, but it also glows in fluorescent light or can be detected through a skin scraping. To avoid getting ringworm in the first place, don't share towels with others and don't walk barefoot in locker rooms or other damp public areas. Make sure you dry all parts of your body completely after showering. If your pet has ringworm, avoid touching it until the fungus has cleared up.
In 2002, a woman named Mary Leitao was frustrated by doctors' inability to diagnose her son's skin problem, which included typical skin parasite symptoms such as crawling sensations and itching. He also appeared to have strange fibers emerging from his skin. Leitao named the condition Morgellons disease [source: Morgellons Research Foundation]. Other people have since claimed to have Morgellons, and also believe that it causes joint pain, chronic fatigue, neurological symptoms and a host of other problems. Leitao founded the Morgellons Research Foundation in 2004, which has more than 10,000 registered self-diagnosed patients. The CDC recently began an investigation to research the disease.
Currently most doctors believe that Morgellons symptoms can be explained by existing conditions, including delusional parasitosis [source: Bohart Museum of Entomology]. This is a mental condition in which the patient believes he is infected by a parasite, but isn't. Psychotropic drugs are typically prescribed to treat this. Those physicians who believe that Morgellons is an actual disease, however, often prescribe antiparasitic medications and antibiotics, as well as special diets and herbs.
Parasites and Perceptions
If reading about skin parasites hasn't left you feeling a little itchy, you're probably in the minority. It may surprise you, however, to know that our thoughts about parasites have changed over the centuries. Many of us also have some serious misconceptions about how people become infested with parasites and what it says about them.
Skin parasites have been around for thousands of years. Lice have been dated to more than five million years ago, as scientists discovered that the lineage of human head lice separated from chimpanzee head lice around the same time that their hosts diverged. Scabies mites date back to at least 2,500 years ago. Scholars believe there are references to scabies and other parasites in the Bible, and the Greek naturalist Pliny gave recommendations for getting rid of lice in his writings around 40 C.E. [source: Roncalli].
Humans have always strived to rid themselves of parasites as part of what some researchers point to as a relic of our animal grooming past. Yet it has not always been considered such a shameful, private affliction. In the past, ridding ourselves of fleas and lice was often a group bonding activity (similar to primates that groom each other), and it still is in some areas of the world. Parasitic infestations did not differ by socioeconomic class -- the difference was that the wealthier you were, the easier it was for you to privately get rid of your parasites. Wealthy people had servants to assist them as well as access to the latest home remedies and hygienic products. It's also important to keep in mind that it took until the 20th century to fully make a connection between cleanliness and health.
Today, getting skin parasites is often associated with being dirty. However, many infestations are simply a case of being in the wrong place at the wrong time. Having head lice, for example, doesn't mean that you don't bathe properly or keep a clean house. You were simply unfortunate enough to come in contact with an infected person or animal. While many parasites are prevalent in less developed countries, providing access to basic treatments, as well as education on preventive measures and hygienic practices, can reduce infestations. Skin parasites can attack anybody; you just have to take steps to ensure that you aren't likely to be on the menu.
For lots more information on skin parasites and related topics, check out the links on the next page.
Related HowStuffWorks Articles
- American Academy of Dermatology. "Scabies." AAD Public Center. 2009.http://www.aad.org/public/publications/pamphlets/common_scabies.html
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- Centers for Disease Control and Prevention. "Lice." May 16, 2008. CDC.http://www.cdc.gov/lice/
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- Larrick, Stephanie and Roxanne Connelly. "Human Bot Fly." University of Florida. July 2008.http://entnem.ifas.ufl.edu/creatures/misc/flies/human_bot_fly.htm
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- Mendez, Andre. "Tungiasis." Stanford ParaSites. 2004.http://www.stanford.edu/group/parasites/ParaSites2004/Tungiasis/index.htm
- Morgellons Research Foundationhttp://www.morgellons.org/
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- The National Pediculosis Associationhttp://www.headlice.org/
- New Zealand Dermatological Society Incorporated. "Scabies." DermNet NZ. February 16, 2008.http://www.dermnetnz.org/arthropods/pdf/scabies-dermnetnz.pdf
- Pollack, Richard and Gary Alpert." Bed Bugs: Biology and Management." Harvard School of Public Health. March 24, 2005.http://www.hsph.harvard.edu/bedbugs/
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- Vredevoe, Larisa. "Background Information on the Biology of Ticks." University of California, Davis. 1997.http://entomology.ucdavis.edu/faculty/rbkimsey/tickbio.html
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- Stewart, J.W. "Common Insect & Mite Pests on Humans." Texas Agricultural Extension Service. March 18, 1997.http://insects.tamu.edu/extension/bulletins/uc/uc-013.html
- Time. "Parasitology: The Human Botfly." Time Magazine. July 10, 1964.http://www.time.com/time/magazine/article/0,9171,871286,00.html
- U.S. Army Center for Health Promotion and Preventative Medicine. "Human Bot Fly Myiasis." U.S. Army. August 2007.http://chppm-www.apgea.army.mil/documents/FACT/HumanBotFlyMyiasisJTFAug2007.pdf