My Husband Broke Out Into Swollen Hives On His Face,

My husband broke out into swollen hives on his face, under his arms, torso, legs and penis after eatting crab last night. He had never experienced an allegey to shellfish prior. I have given him 4-6 doses of benadryl today with very little reduction in hives. He believes its worse and is now having difficulty urinating. What should I do?