Although I have not been on Keytruda I have had rash a lot with Tafinlar and Mekinist along with bleeding inside my nose. I have had great success with Aquaphor that does not have petroleum in it. I have heard great things of coconut nut oil but have not used it myself. I did breakout a lot when I first started Tafinlar/Mekinist combo and was able to get more help from my dermatologist. You may want to give them a shout for help.
I wish you the best controlling the side effects because that is so important to stay strong.
Take care
