Teething

Teething occasionally may cause mild irritability, crying, low-grade temperature (but not more than 100 degrees Fahrenheit), excessive drooling, and a desire to chew on something hard. Usually, the gums around new teeth will be tender and swell.
To ease your baby's discomfort, the American Academy of Pediatrics recommends that you try gently rubbing or massaging the gums with one of your fingers. Teething rings are helpful, too, but they should be made of firm rubber.
Pain relievers and medications that you rub on the gums usually aren't useful, since they wash out of the baby's mouth within minutes. If your child seems particularly miserable or has a fever higher than 100 degrees, teething probably isn't the cause. You should consult your pediatrician as soon as possible.