I have a skin condition named Psoriasis. It's usually pretty tame, but some days the itch is constant and very distracting from work. I can barely concentrate and get much done in the day because I'm constantly scratching my scalp and cleaning my desk from all the dandruff it produces.
Sometimes the itching is so severe that I need to take sick leave for the day. My manager is aware of my condition but maybe not the severity of it. Also, I do not need a doctor's note, but it feels unprofessional to leave due to "itchiness" even if it's intense.
How can I approach my manager about needing to leave work due to my condition?