...that's a great question and one that is a little difficult to answer. I think we are all different when it comes to how quickly and severely we respond to the cream. There are many factors--the area you are treating, the amount of damage you have, the frequency of application, and the amount of cream you apply. It is quite possible that you are one of the lucky ones who will not have a severe reaction to the cream and your side effects will be minimal.
From my own experience treating my chest and face, a week and a half to two weeks is the typical length of time it takes for me to see any real redness and irritation begin. This may be right on track for you when it comes to scalp treatment.
Hang in there! Don't hesitate to reach out to us if you need us--we are always here for you!
I am including the link to an article that offers tips for using the cream.
https://skincancer.net/life-with-skin-cancer/tips-for-efudex-users
Sending you positive thoughts for wonderful results!
April, SkinCancer.net, Moderator