Instead of shooing away your dog the next time he noses around your baby, you might want to reward him for the medical service he is providing.

Recent studies show that children under 1 year of age who regularly play with outdoor dogs eventually build stronger, healthier immune systems. The dogs in the studies spent about 18 hours outside daily and trailed dirt and other antigens inside. The theory is that this exposure accelerates the pace at which babies develop mature immune systems, resulting in fewer ear infections and less antibiotic therapy. A similar but less dramatic phenomenon is seen with cats, likely because fastidious felines groom away much of the debris before babies are exposed.

So the next time your baby wants to pow-wow with your pooch, you might just want to let nature take its course.