Hi.. Can understand your concern.. As per your complain it seems that you have got an allergic reaction to something like some food product or any insect bite (which could have accidentaly entered your mouth leaving the poisonous sting there leading to allergic reaction) , some chemical in the drinking water or other beverages can also cause this or intake of certain medicine can also be the cause. In case of sudden swelling you should consult an emergency room in hospital as sudden swelling in tongue can lead to difficulty in breathing and swallowing as well as it can lead to other severe complications which can be life threatening.. As taking prednisone tablet has ceased growing of swelling as it is a steroid and relieves symptoms of allergy but it has to be taken into notice that finding the cause of swelling is must to avoid future complications.. I would suggest you to consult a doctor and get evaluated so that he can find the cause of swelling and give appropriate treatment to avoid future complication and recurrences. Hope your query is solved.. If you find the answer helpful please write a positive review and click on find this answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora.