What Is The Treatment For Hives?

I have gotten hives three times in four months. The first time was in August, it lasted for a week and came during the middle of the night. The second time was four week later, it lasted for 2 or three days and started about 9 in the morning. The third time showed up today around noon. All of the hives are in the same spots. On my knees, elbows, wrist, and left lower part of my torso. Whenever they come up my fingers,feet, and toes get swollen. I have seen an allergenist and found out im allergic to grass. but I havent been outside for a couple days. Also I used to take bennedryl and it helped alot for the first two cases but it hasn't worked today at all. My mom thinks i have a virus. Do I? If so what is it? How can I treat it?