THERE could be thousands of microscopic creatures crawling around inside your body right now.
It's a gross thought, but it's actually more common than you might think.
There are several bugs that frequently feed off human blood before laying eggs underneath the skin.
It's often nothing to worry about, but it can lead to life-threatening infections.
Professor Adam Hart, ecologist, conservation scientist and entomologist at the University of Gloucestershire, said: "Lots of creatures see us as a potential place to live, and in some cases to raise a family.
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"If they cause harm, then we call them parasites.
"Laying eggs in or on us may seem gross, but parasites are a fact of life for all animals, especially large animals like us."
Here are seven pests notorious for making themselves at home on your body, and making room for the next generation.
1. Lice
One of the most common bugs to live on humans is lice.
They can be found on the body and in the hair and they feed on your blood.
Sometimes, their eggs can be located just beneath the skin.
Lice spread through direct contact and can cause irritation, infections and transmit diseases like typhus.
They are treated with over-the-counter and prescription drugs.
The most common signs of lice are:
- Visible bugs
- Itching
- Crawling sensation
- Swollen glands
- Pink eye
- Sores on the scalp, neck and shoulders
2. Tapeworms
Tapeworms go more than just skin deep.
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The flat, ribbon-like creatures, which can reach more than 23ft in length, invade your gut and lay tens of thousands of eggs while they're there, Professor Hart said.
When these hatch, they can spread throughout your body, to your lungs, liver and even your brain.
People often don't experience symptoms, but they may notice worms in their poo.
Other signs include:
- Stomach pain
- Diarrhoea
- Feeling sick or vomiting
- Loss of appetite or increased appetite
- Weight loss
- Headaches
- Yellowing of the skin and eyes
- Cough or shortness of breath
- Vision problems
Several medications easily kill tapeworms, and any remaining creatures will eventually pass in the toilet.
Prevention techniques include frequent hand-washing, wearing shoes on soil containing worms, only drinking bottled water in high-risk areas, and not eating raw or undercooked beef, pork or freshwater fish.
3. Loa loa
Another rather grim-sounding bug is the Loa loa, or roundworm, which is passed onto humans through horse flies.
When the flies bite, the larvae, or white maggots, enter your body and grow beneath your skin for around five months.
They then release thousands of eggs a day, which travel throughout your body.
Sometimes, it is possible to see the worms moving under your skin or across your eyeball.
This is known as loiasis. Severe infestations can lead to inflammation of the brain, coma and even death, Healthline reports.
Most people don't develop symptoms, but you might experience:
- Itchy or painful swelling
- Worms across your eyes
- Muscle or joint pain
- Fatigue
Eye worms can be surgically removed, while other infections can be treated with medication.
4. Onchocerca volvulus
The Onchocerca volvulus parasite spreads through bites from black flies, commonly found near fast-flowing streams and rivers.
Once inside the body, they spend six to 12 months in the bloodstream and subcutaneous tissue before releasing their eggs.
Infection can cause an eye and skin disease known as onchocerciasis.
Symptoms, caused by the microfilaria which move around the body, include:
- Itching
- Rashes
- Raised nodules
- Blindness
An antiparasitic drug, usually ivermectin, is used to treat the problem.
5. Human itch mites
Sarcoptes scabiei - also known as human itch mites - are microscopic bugs that live on their hosts, which unfortunately can mean human flesh.
Adult female mites tunnel into the top layer of skin and can remain there undetected for weeks.
Even more disgustingly, they often lay eggs, Professor Hart says.
Mites are typically invisible to the naked eye so people usually don't notice them until raised marks appear on their body.
An itchy red rash or spots can also develop - two common signs of the skin condition scabies.
The most frequently reported symptoms include:
- Red, rash-like marks
- Small bumps that can become hard or inflamed
- Irritation
- Itching - particularly at night
- Pain near the mark, rush or bump
- Swollen or blistered skin
While uncomfortable and fast-spreading, scabies can usually be cleared with a cream or lotion.
6. Human botfly
Dermatobia hominis is a species of botfly whose larvae infest humans as a parasite.
Native to Central and South America, they glue their eggs to mosquitos and other blood-sucking insects.
When the mozzie bites a victim, the creamy-coloured eggs hatch and the larvae make their way into their skin.
They can dig up to two inches into human flesh before feeding on muscle.
Painful, pus-leaking pimples then form, which baby bot flies feed off for the next five to 10 weeks, Professor Hart said.
The infestation of any fly larvae inside the body is known as myiasis.
Common symptoms include:
- A lump under the surface of the skin
- Larvae moving under the skin
- Itching
- Skin irritation
- Abdominal pain
- Vomiting
- Diarrhoea
- Larvae in your poo
To treat myiasis, the larvae need to be removed by a medical professional then the area kept clean, WebMD reports.
7. Face mites
Thousands of tiny mites live around the face, eyelashes and even nipples of almost every person on Earth.
They burrow into your pores, eat your natural skin oils and climb back out to mate while you're asleep.
But it doesn't stop there. After having their wicked way with one another, the bugs return to your pores to lay their eggs.
While pretty gross-sounding, the process is relatively harmless, according to Professor Hart.
It only becomes problematic when there are large numbers on the face, which can contribute to conditions like rosacea and demodex folliculitis, dermatologist Scott Walter said.
According to the Cleveland Clinic, the most common symptoms are:
- Burning sensation
- Itching
- Pustules that look like whiteheads
- Redness
- Rough feeling on your skin, like sandpaper
- Scales, perhaps resembling eczema
- Sensitive skin
- White sheen on your skin or eyelashes
- Decreased vision
- Eye irritation and itchiness
- Loss of lashes
- Thickened or scaly eyelids
Treatment involves cleaning the face regularly and using various medications to kill the mites.