It is not an allergy. That happens to me with celery too.
Steve Mack, Post-Doc Fellow in Molecular and Cell Biology Roche Moceular Systems says:
“To start, here is a list of all the chemicals found in celery. Many of these have a broad range of activities, but I’ve narrowed things down into three categories of compounds. Third, and I think most likely, is the compound Eugenol. This is the active ingredient in Clove Oil, and is used in temporary dental fillings to deaden the nerve pain of a cavity. The numbness that you experience from celery might be due to the numbing effects of Eugenol on your tounge.”