Teething in babies in another milestone both for the baby and for the parents. Teething can occur as early as 4 months to 24 months and it can be an irritating/discomfort feeling for some babies while some don’t show any signs at all. Many parents associate teething with fever and diarrhea, but researchers say these symptoms aren’t indications of teething. The two bottom front teeth are usually the first to appear, followed by the two top front teeth.