New to UC-need some advice

My son was diagnosed with pancolitis this last May after taking Cephalexin for acne. After spending a week in the hospital and most of the summer on pred and asacol he at least has recovered enough to go back to college and return to his job. Just recently he has had a mild flareup which has become severe because our family doc put him on Benzaclin for his acne which had become extreme due to the Lialda. He has used it for 4 days and while his acne is better his UC has really flared up with lots of blood. I decided to read more about the Benzaclin tonight and discovered that it can cause colitis! Our doc knows of his condition and assured me before she saw him that she would be very careful with what she prescribed. His GI doc doesn't deal with acne problems and told us to see our family doc. I am so frustrated I don't know what to do! My son is becoming very depressed and is completely fed up with all of the doctors. Does anyone have any ideas of an acne med that will not aggravate the UC?? The severe acne bothers my son almost as much as the UC. He has tried a lot of different meds-Differin,Pro-Active and other topical meds.

I've read that probiotics can prevent the yeast that these anti-bacterial medicines can allow to proliferate, which can be the culprit in UC.
But I don't know if they would negate the benefits of the medicine.
To be safe, stick to topicals??
I believe my UC was caused by Accutane, the timing and evidence is compelling. Sad.