I confess to being a tanning person. The only Crohn's drug I've seen on their list (or noticed as making more sensitive) is Cipro. I've been on steroids for 7 out of the last 9 months and never had an issue tanning except with the Cipro. Here's a link with a list of sun-sensitive meds: http://www.medicinenet.com/sunburn_and_sun-sensitizing_drugs/page8.htm
Just noticed MTX on the list...