• Fever, irritability, lethargy, persistent crying, or difficulty breathing. All of these can be signs of illness.

• An upper respiratory illness such as bronchitis or influenza. If your child has a fever, too, he should definitely stay home. The common cold, on the other hand, isn't reason enough to stay home.

• A gastrointestinal illness. A child with diarrhea that can't be contained by diapers or by using the toilet regularly should stay home until his condition improves. Also, children whose stools are bloody or have mucus in them should stay home; it could be the sign of a viral or bacterial infection. (Give your pediatrician a call!) A child who is vomiting persistently should also skip child care or preschool until he's better.

• A rash, though only if you're sure it's linked to an infection (many aren't). If your child's rash is not linked to a fever or other symptoms he can probably go to preschool or child care. What's more, if a rash is associated with an illness (usually a virus) rather than dry skin or a condition such as eczema, the peak of contagiousness has usually passed by the time the rash appears, and your child can go to preschool or child care.