Can I wear a skull cap 20 days post FUE?

Do not put pressure or touch the recipient region for 14 days at a minimum.   Follicles are tremendously sensitive and completely reliant on surrounding perfusion pressure to deliver them nutrients and remove waste.   A skull cap will restrict blood outflow from the scalp and lead to congestion. 

You can wear a cap the very next day of your surgery, as long as it does not exercise a pressure on your head.