How Can Hives On The Shoulder Be Treated?

Hi. I have broken out in hives around my right shoulder and shoulder blade. This happened after planting a small garden in my yard. I must have gotten a bite, but it is all over my shoulder now. This happened on Monday. I am getting no relief and going crazy; so uncomfortable. Took some Benedryl last night, just one kaplet, but doesn't help much. I am 59 years old. Pls. help.