Have you ever met someone who kind of irritates you at first? Then later, as you get to know him, he sort of grows on you? It’s actually a pretty pleasant sensation when you realize that someone you previously disliked is now a good friend. It’s a shame that not all things that grow on you are equally nice.

Take lowly fungi, for example. They’re usually not too bad. In fact, fungi do a lot of work for us. Yeast helps ferment things and gives bread dough a nice lift, and mushrooms can be delicious in a salad or on a burger. But toenail fungus? Not such a good thing. In fact, it can be downright gross.

Toenail fungus is most often a mold-like fungus, and is usually caused by the same microorganism that causes athlete’s foot (an itching, burning infection of the skin). In fact, an attack of athlete’s foot may lead to an infection in the toenails.

Because fungi tend to thrive in moist, dark environments, you’re more likely to find them lurking where things are nice and damp, and where plenty of people are walking around, sharing their fungal infections with everyone. Swimming pools, locker rooms, and showers definitely fit the bill. You’re also more likely to develop a fungal infection if you tend to have sweaty feet (which keep your socks and footwear damp, thus providing an ideal environment for fungal growth). Wearing closed-in footwear (like men’s dress shoes or blocks of concrete), or having small injuries in your skin or nails may also make you more susceptible.

Fungal infections in your toenail may start off as a white or yellow spot at the tip of your nail. As the infection progresses, it will likely spread into the nail bed, causing your nail to become thickened or even distorted, discolored (usually yellow or brown), and sometimes kind of stinky. The edge of your nail may become crumbly or brittle, and the nail itself may lose its luster or shine, and you may also notice that debris begins accumulating under your nail, which may give it a dark color. Over time, your nail might also begin to loosen from the nail bed. (Plus, if you listen very closely, you may hear the faint, maniacal laughter of the fungus as it invades your body. It usually sounds something like: “Mwhahahahaha.”)

Fungal nails aren’t the only type of foot problem that can cause the above symptoms. That’s why it’s important to get an accurate diagnosis from your friendly neighborhood podiatrist. Of course, it’s always best when you go to see your doctor as soon as possible after experiencing symptoms. Unfortunately, fungal nail infections can go on for years without treatment. You might simply not notice it, or you might ignore the infection because it isn’t causing any immediate pain. Unfortunately, fungal nail infections tend to be more difficult to treat the longer they’re around, so visit your podiatrist sooner rather than later.

In order to make a firm diagnosis, your podiatrist will likely inspect your toenail and may take a scraping of the nail (which will be cultured or examined under a microscope) in order to find out whether or not you really have fungi growing on you.

Some minor cases of fungal infections may improve over a period of months as you keep your toenails dry and clean. There are also over-the-counter treatments available, although their success rate isn’t always very high. These treatments tend to be liquid fungicides that you can apply to the surface of your toenail.

Your podiatrist may prescribe topical ointments. Prescription oral treatments are also available, and are likely to be more effective in getting rid of those too-friendly moldy hangers-on of yours. These treatments tend to clear up fungal infections about half of the time (which, considering the success rate of other treatments, really isn’t too bad). Unfortunately, there are also often side effects connected with oral anti-fungal medications. Be sure to discuss all risks with your doctor.

In serious cases, your podiatrist may suggest surgery. The nail will likely be removed in order to allow anti-fungal treatments to be applied directly to the nail bed. Ideally, when the nail grows back, it will be fungi-free.

Whatever their other qualities are, fungi tend to be persistent little fighters. So, be prepared for further outbreaks. Keeping your feet clean and dry, changing your socks when they’re sweaty or otherwise wet, and allowing your feet to breathe regularly (by wearing open shoes or shoes made of breathable materials) will help keep these clingy nuisances away.