Most babies spend a considerable portion of the second half of their first year getting teeth. The first to erupt are usually the two lower central incisors, followed weeks later by the two upper central incisors and the two upper lateral incisors. The baby may chew on his hands or on teething toys and seem a bit irritable for weeks before a tooth actually erupts. Some babies have a little nasal congestion during this process.
A normal baby may have many illnesses in the first year. Illnesses and periods of teething may overlap. Many people believe that the teething process causes illnesses or fever. This theory has been studied, and has never been found to be valid. Probably the true story is that teething and illnesses with fever are independent processes that frequently occur simultaneously. The point of this all is that if your baby has a fever, you must assume he is ill; do not automatically attribute the fever to teething. This is particularly important when a baby younger than age three months has fever, and you should consult your doctor quickly if this happens.