Skin Parasites

Ticks

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.

Lyme Disease and Rocky Mountain Spotted Fever

Many ticks carry a bacterium that causes Lyme disease. The disease initially causes muscle weakness, depression, headaches, fever and a circular "bull's eye" rash around the tick bite. If not treated, the infection spreads through the bloodstream and can lead to Bell's palsy, meningitis, swelling of the brain and loss of motor function. If caught early and treated with antibiotics, most people who get Lyme disease experience mild symptoms. However, these symptoms may take up to a year to completely go away.

Rocky Mountain spotted fever is also a tick-borne infectious disease. Despite its name, it occurs in almost every state in the United States. Symptoms include muscle pain, headaches and fever, followed by a widespread, spotted red rash. It can be difficult to diagnose, as not all patients get the rash. If not properly diagnosed and treated with antibiotics immediately, the disease can lead to long-term organ damage requiring amputation, hearing loss and partial paralysis. A small percentage of people with Rocky Mountain spotted fever die of complications.