What Causes Hives At The Place Of Physical Contact?

I think my boyfriend gives me hives. Lately after prolonged physical contact with him, I get hives on my body where he touched me. Just a few minutes ago he was resting his chin on my arm and when he moved, I had hives where his chin was.

We have been dating for almost three years and this has not happened until a month or two ago. What do I do?