The new backpacks are broken in, the homework routine is set, and kids seem to be getting into the groove of a new school year. Everything is going predictably when you get a call from the school nurse: "You need to pick up your child."

He went the whole summer without so much as a sniffle. Now, when he can't afford to miss school and you can't afford to miss work, he's sick. WebMD talked to medical experts about common ailments you can expect during the fall term, how to prevent them, and the latest information on immunizations.

When is Your Child Too Sick for School?

The Leading Ailments

Allergies. Fall is prime time for ragweed, molds, and other allergens. Kids with hay fever can still walk around and play sports, but the sneezing fits, itchy eyes, and fatigue can make them miserable and distracted. Your child's doctor can prescribe medication to manage the symptoms, and you can help your child avoid allergens. Wash bed linens weekly, avoid opening windows in your home and car, vacuum carpeting and rugs regularly, and keep kids from playing in piles of dead leaves.

Asthma. "Asthma is the leading chronic disease when it comes to kids missing school," says Michael Posner, MD, FAAP, spokesman for the American Academy of Pediatrics (AAP). Asthma is generally treated with preventive medication. The effectiveness of inhaled steroids or long-acting medications increases with use over time, reducing the likelihood that a respiratory infection or environmental changes will trigger asthma. "When kids show improvement, some parents think they're over the asthma, when in fact it's the medication keeping them well. Parents need to understand that kids must continue using the medication."

Develop an individualized asthma action plan with the school nurse, says Amy Garcia, RN, executive director of the National Association of School Nurses (NASN) in Silver Springs, Md. "Make the nurse aware of triggers, symptoms, medications, and what works with that child."