Ron Howard blames his hair loss on anxiety over Henry Winkler becoming more popular on Happy Days
https://www.dailymail.co.uk/tvshowbiz/article-10083355/Ron-Howard-reveals-hair-loss-anxiety-Fonz-eclipsing-character-Happy-Days.html
In his new memoir with brother Clint Howard, The Boys: A Memoir of Hollywood and Family, the actor/director detailed how he developed a stress-induced skin condition that resulted in his hair "falling out in alarming clumps" during the early years of Happy Days. "It did not escape my notice that as the season went on, the Fonz was getting more and more screen time," Howard writes. "I didn't handle my stress particularly well. I probably would have benefited from seeing a psychotherapist … Instead, I kept everything inside." Howard stresses his anxiety was over the Fonz, not Henry Winkler.