Parents, if your child suddenly develops a skin infection, get prompt attention from a skin specialist.

"Proper diagnosis is especially important for treatment because some home remedies -- like over-the-counter cortisone -- can make an infection worse," says Jody A. Levine, M.D., head of pediatric dermatology at Montefiore Medical Center in New York City.

Her advice on the four top -- and highly contagious -- skin conditions in children:

Impetigo. When kids rub their runny noses and develop a honey-colored crust, or when diaper rash erodes the skin, the staph and strep bacteria that ordinarily live on the top of the skin get in deeper and cause infection. To prevent spreading: Protect the skin. Use petroleum jelly or zinc oxide ointment on the nose, lips or diaper area; cut children's nails short; don't share washcloths or towels.

Molloscum. Shiny pimples caused by a virus can spread from one area of the body to another. To prevent spreading: Don't share towels; disinfect showers; avoid picking or squeezing the pimples.

Warts. They are infectious, but not everyone gets the virus. Plantar warts appear on the soles of feet. To prevent spreading: Keep warts covered; wear sandals while in the shower.

Ringworm. The fungal infection tinea likes warm, moist areas of the body. To prevent spreading: Dry off thoroughly after swimming or sweating; disinfect any brushes, combs, hats and helmets, and don't share them; examine and treat pets (cats, in particular); practice good hygiene