Dr. Greene: Here is the ABC and the XYZ of maintaining and promoting immune function.

Avoid Unnecessary Antibiotics and Antibiotic Soaps. The more kids use antibiotics, the more likely they are to get sick more often, with longer, more stubborn infections caused by more resistant organisms.

Breastfeeding. Breast milk is known to protect against gastrointestinal tract infections, otitis media, invasive Haemophilus influenzae type b infection, RSV infection, and other causes of upper and lower respiratory tract infections - even years after the breastfeeding is done. Kids who don't breastfeed average 5 times more ear infections.

Cigarette Smoke. Keep your child as far away from it as possible! Exposure to second-hand smoke is responsible for many health problems, including more than 2 million unnecessary ear infections each year in the United States.

Sleep. Late bedtimes and poor sleep leave children vulnerable.

Vaccines. Prevnar and the flu vaccine are particularly helpful for protecting children from common infections in daycare.

Water. Getting plenty of fluids supports immune function.

Xylitol. This is a natural, non-sugar sweetener (found in raspberries and plums) that has been proven to prevent ear infections, sinus infections, and tooth decay. It is available as chewing gum, mints, and in a powder form.

Yogurt. The beneficial bacteria in active culture yogurt can help prevent tummy aches, diarrhea, food poisoning, food allergies, eczema, sinus infections, bronchitis, pneumonia, and colds - among other things!

Zinc. Children who are zinc deficent get more infections and stay sick longer.