Alopecia areata universalis is the loss of hair over your entire body. diffuse alopecia areata is a sudden thinning of your hair rather than lost patches. Alopeciaareata is an autoimmune disease, which means the hair loss is caused by your immune system mistakenly attacking your hair follicles. scientists aren’t sure why this happens, but the fact that alopecia areata sometimes affects members of the same family suggests that genetics are a risk factor. Alopecia Areata Symptoms 9 Natural Treatments Dr Axe Alopecia areata is an autoimmune disease. this means that your immune system mistakenly attacks a part of your body. when you have alopecia areata, cells in your immune system surround and attack your hair follicles (the part of your body that makes hair). this attack on a hair follicle causes the attached hair to fall out. The course of alopecia areata is one of spontaneous remissions and recurrences. although patients with this disorder are usually otherwise healthy, some have co...