According to US Department of Health and Human Services, alopecia areata is condition that happens when the immune system attacks hair follicles and causes hair loss.
In alopecia areata, the immune system mistakenly attacks hair follicles, causing inflammation. Researchers believe that both genetic and environmental factors play a role.
Health experts have classified the hair loss condition in three types: – Patchy – Totalis – Universalis
source: NDTV
The actor first revealed about her condition publicly on her Red Table Talk series in 2018. She said it "was terrifying" to deal with when alopecia first started.
Pinkett Smits also said that she used to find “handful of hair” while taking shower. She went on to say that she then decided to cut her hair. The actor debuted her shaved hairstyle in July 2021.