Pinkett Smith's hair loss from alopecia at center of spat

Actress Jada Pinkett Smith's hair loss is at the center of the most talked-about moment at Sunday's Oscars ceremony.

Smith disclosed four years ago that she has alopecia and it's the reason she has shaved her head or worn turbans in public.

The autoimmune disease attacks hair follicles.

It's unclear if comedian Chris Rock knew about it when he joked about her baldness during the ceremony.

But his comment prompted a smack and profane admonishment from Smith's husband, actor Will Smith.

The National Institutes of Health says alopecia affects all racial groups, men and women equally.

There is no cure.