Why does raw celery make the mouth feel numb?

For years people have recognized the natural effects of celery in "calming the nerves." Celery. In fact in the 1897 Sears Catalog the company offered a nerve tonic made from celery. And before that Hippocrates (the father of medicine) noted that celery calms the nerves. Celery is high in calcium and it is widely recognized for its medicinal effects.

Most likely the numbing effect you're noticing is from the Eugenol in the celery. It is the same compound found in higher concentrations in cloves.