I've never been on Asacol, but had the same problem over the summer this year. I was on predn "only" for 2-2,5 months and had started Lialda during that time. Two, three weeks after tapering predn my hair went crazy. I was literally shedding. Even though I have short hair, after few weeks my DH noticed that something was wrong. A man, he isn't supposed to notice that kind of thing
What was worse, I was overseas for the whole summer, and had no contact with my doctor. Was really worried that it was Lialda side effect and I would finish being bald in a couple of months. After being back to US I saw my GI and dermatologist. They both said that it can be due to several reasons: flare-up taking its toll, predn - taking its and Lialda - on top. Moreover, I got seborrheic dermatitis sometime in the course.... Yay! Lucky me! But both of them were quite positive that it would pass. Esp dermatologist was pretty sure that my hair would grow back, he already saw some new hair coming through (I've believed him, even though I couldn't see them). He just put me on Biotin 5mg per day. And now, voila!
I've been taking Biotin since the beginning of Sept this year (and Lialda, cont) and my hair already looks better, a lot thicker. And since I have short hair, I can already feel the difference. Seborrheic dermatitis is still there, and the medicated shampoo is not a gentle one, that for sure. I also color hair every 4-5 weeks top and still, they are coming back.
If you can, start Biotin, as for me, it's obviously helped. Even if hair was to grow back any way, the biotin made it faster and right now, I almost don't see any loose hair at all. Hope it helps you too.