Common household pets, such as dogs and cats, can carry ringworm, which causes scalp fungus. You can pick up the condition just by touching these animals -- ringworm can transfer to you from contact with an animal's fur or skin. If a dog or cat has a bald spot, it could be a sign of a ringworm infection [source: Centers for Disease Control].
While you should keep in mind the risks posed by animals infected with ringworm, you're more likely to pick up the condition from another person. Ringworm can live for several months on items like hats, scarves, brushes, combs and other items that touch your scalp. To avoid infection, try to avoid sharing these items with other people. Even if someone's scalp looks healthy, he or she could be carrying scalp fungus without showing any symptoms [source: WebMD].
The best way to steer clear of scalp fungus is to avoid situations where you could pick it up from another person or animal. Good hygiene is important, too -- scalp fungus thrives in areas that are damp and moist, so be sure to wash the sweat out of your hair when you come back from a workout. Also, be careful if you have a cut or scrape on your scalp, because this is a prime spot for the fungus to enter your body. Be sure to wash any cuts or scrapes thoroughly [source: Berman].
Despite all your best efforts at prevention, sometimes it just doesn't work. For information on how to treat scalp fungus, read the next page.