Hi, I have tried many times to use fluoroucil and feel too ill to continue. The blistering doesn’t bother me, it is the fatigue that I get just from covering just small lesions, not a large area. The dermatologist said that I have a systemic reaction unfortunately. I feel like I have flu whilst using it and it triggers my migraines. I can’t use it now. Was prescribed Aldara but was worse with that. It could be something to do with DPD deficiency. Cancer patients who are prescribed this drug for IV are supposed to have a test to see if they have this deficiency but they don’t do the test for topical use. Out of interest are you highly sensitive to medications because I am.