Lili Reinhart has shared that she was recently diagnosed with alopecia. The 'Riverdale' star took to TikTok on Monday to post a video of her undergoing red-light therapy, writing, "Was just diagnosed with alopecia in the midst of a major depressive episode." According to the National Institute of Health, Alopecia occurs when the "immune system attacks hair follicles and causes hair loss," It typically affects the head and face but can cause hair loss from any part of the body.