follicle

Alopecia is caused by the immune system mistakenly attacking hair follicles at the root of the hair, causing it to fall out.

Also called cicatricial alopecia, the condition causes permanent hair loss after the immune system attacks and destroys the follicles.

Celebrities including Jada Pinkett Smith and Louis Theroux have been praised for sharing their experiences with alopecia - a disease that occurs when the immune system attacks hair follicles and causes hair loss.

“They destroyed every bloodstain, every hair follicle, every shred of physical evidence which might tell us what those officers did inside the apartment to kill the boy,” he said.

Alopecia areata, which affects more than 6 million Americans, occurs when the body's own T cells attack hair follicles, leading the hair to fall out.