Hives on scar?

Bearfootz

It's been over three years since my c-section and I'll still wake up sometimes with a random hive or two along the incision line.  I've noticed it a couple times since I found out I was pregnant again. (In fact I had one the day of my bfp, and then again this morning)

Has anyone else had this?  Just wondering if it's a random event or if there's some explanation for it.