Get full access to Outside Learn, our online education hub featuring in-depth nutrition, fitness and adventure courses, and more than 2,000 instructional videos when you sign up for Outside+..
You probably assume that parasites are a problem only if you’ve traveled to remote regions with iffy sanitation. But they’re way more common than you might think. Millions of Americans have parasites, and some types infect as much as five percent of the U.S. population. Here’s what you need to know about those bad bugs—and how to banish them, for good.
Who’s at risk?
“Parasite” is a broad term that describes any organism that lives and feeds off another organism, including lice, giardia, and even mosquitoes. Intestinal parasites—including worms (known as “helminths,” usually visible without a microscope) and protozoa (microscopic, single-celled organisms)—specifically reside in the gut. Pinworms are the most common parasite in the U.S., living primary in the large intestines. Giardia is the second-most frequent domestic parasite. When it’s swallowed, it makes its way through the digestive tract, splitting into two hungry microorganisms that attach to the walls of the small intestines. Other parasites, such as hookworm and whipworm, are less common in the U.S. And while you’ll hear plenty of horror stories about tapeworms—flat, segmented beasts that can grow as long as 50 feet—they’re relatively rare. You’re probably at risk only if you’ve traveled to a developing nation or work closely with livestock.
Intestinal parasites are usually contracted from eating undercooked meat from an infected animal, or from raw fruits and vegetables that have been contaminated. Giardia is commonly water-borne. It lives well in cold streams, so if you’ve been drinking that “clean” mountain water on your backpacking trip, you’re likely at risk. You can also pick up parasites through direct contact with contaminated soil and feces, or indirectly from contaminated objects such as bathroom handles or children’s toys.
Signs and Symptoms
Once they’ve been introduced into your body, these freaky organisms travel into the warm, moist environment of the intestines, where they’re more than happy to hang out, feeding on nutrients, growing, and reproducing. Because they’re so well-adapted to the human body, they can live in your intestines for months or sometimes years without noticeable symptoms. And when they do cause problems, they may be tricky to pinpoint. Five signs that might mean you have an intestinal parasite:
- Your gut is a mess. If your normally efficient digestive system grinds to a sudden halt, it could signal an intestinal parasite—especially if you’ve recently been camping or traveled to a developing country. Parasites can cause unexplained constipation or persistent nausea, gas, or bloating. The most common signs of giardia infection (called giardiasis) include diarrhea, stomach cramps, nausea, and foul-smelling, greasy poop. Left untreated, it can lead to dehydration and sometimes significant weight loss. Ongoing giardiasis is linked with a higher risk of irritable bowel syndrome (IBS), lasting as long as six years after the infection.
- You’re really itchy down there. Unexplained, persistent itching and irritation around your sensitive bits can be a sign of parasites, especially pinworms. Once they’re ingested, the eggs hatch in your intestines and grow into adult worms. Female pinworms emerge from the opening of your rectum and lay thousands of eggs in the skin folds around the anus and perineum, making you scratch like crazy. The eggs may also migrate to the vaginal opening, causing irritation and relentless itching. Even worse, if you’re scratching, the eggs may cling to fingers and nails, and you can transfer them to other surfaces. While they’re gross, they don’t usually cause major problems. However, in rare cases pinworms may lead to infections in the uterus and vagina, or increase the risk of urinary tract infections.
- You’re sore and achy. Painful, aching muscles or joints, even when you haven’t worked out or strained anything, can be a sign of parasites. Some varieties of tapeworm and other parasites not usually found in the United States are the most frequent culprits, so you’re probably not at risk unless you’ve traveled to a less-developed region. But research suggests that a wide range of other parasites may be associated with muscle aches, pain, and inflammation, and there’s a known link between roundworm infection and arthritis. Nutrient deficiencies caused by parasites may also impact muscle function, and dehydration from giardiasis can lead to muscle cramps, spasms, and pain.
- You can’t sleep. If your typically sound slumber is suddenly disturbed, it could be a sign of parasites. Pinworms that cause itching can interrupt sleep, making you wake all through the night and disrupting your natural sleep-wake cycle. If you’re a normally heavy sleeper, you may not even notice you’re itching—just that you wake up for no good reason. Other, less common, parasites can actually alter your biological clock, shortening sleep time. And some research links nocturnal bruxism (grinding your teeth at night) with parasitic infections.
- You’re exhausted all the time. Do you feel chronically drained, depleted, and foggy, even after plenty of sleep? It could be a sign of parasites. Intestinal parasites interfere with nutrient absorption and disrupt gut bacteria, leading to fatigue, exhaustion, apathy, and brain fog. Parasites can damage the villi—delicate structures lining the intestinal walls that play a role in nutrient uptake—lessening the absorption of protein, fat, vitamins, and minerals. Some, including giardia and hookworm, are linked with a higher risk of anemia, associated with weakness and fatigue. And giardiasis increases the risk of chronic fatigue, even years after the initial infection. Disruptions to the gut microbiome can also impact mood and cognitive function.
What to Do
If you suspect you have a parasite, get tested pronto. Most doctors will order a stool test for parasites, or ask you to do a “tape test,” which involves sticking a piece of clear tape to your anus, then gently peeling it off. Pinworm eggs will stick to the tape, and can be identified under a microscope. Blood tests also pinpoint antibodies or parasite antigens produced when the body is infected and the immune system is fighting off the invader.
The good news: most intestinal parasites don’t cause lasting harm, and they’re treatable. Check with your physician, then try these simple tips:
- Stick to a whole-food, fiber-rich diet to encourage elimination; steer clear of sugar and refined carbs, which are shown to harm beneficial gut bacteria.
- Baby your belly with naturally fermented foods that are rich in good bacteria, or take a high-quality probiotic supplement.
- Eat raw garlic, the traditional go-to for killing parasites; other antiparasitic foods include pumpkin seeds, raw honey, and ginger.
- Hydrate like crazy to prevent dehydration, promote bowel movements, and help flush those nasties out of your system.
- Use natural antiparasitic herbs such as neem, clove oil, black walnut extract, triphala, or grapefruit seed extract; look for capsules or tinctures, or try a combo parasite detox formula.