...I wish I had seen your question sooner! You are likely feeling the effects by now with redness and itching. You may even be noticing that your skin is tightening as the cream begins to do its job.
The effects felt from Efudex are different for different users and the length of time it takes to start feeling them varies. I have seen everything from a few days to several weeks. I notice a slight tingling the first time I apply the cream but don't see a real redness appear until the end of the first week. Some users report intense reactions right away and others say they don't notice anything at all for weeks. I believe our skin types and the level of damage all factor into our reactions.
I hope you are getting rest and your daily activities aren't impacted. I have never treated my hands or arms, but I have seen others who have.
I am including a link to an article that might help as you finish up treatment. https://skincancer.net/life-with-skin-cancer/tips-for-efudex-users/comment-page-1/#comments_anchor
Here's one you might find handy as you enter the healing stage. It can be particularly difficult.
https://skincancer.net/life-with-skin-cancer/efudex-side-effects-tips/
Please keep us posted on your progress. Sending you positive thoughts as you heal! I know what it's like--you are not alone in this!
April, SkinCancer.net, Moderator