My 11yr old son had an episode of alopecia areata for a short time earlier this year. I panicked as he is still a young boy so went straight to a homeopath who took him off his regular diet and straight onto what was missing in his body which was magnesium, B vitamins, possibly iron (not tested) and some others I cannot remember. One thing that she stressed was to eat BROWN rice and NOT WHITE RICE as white is virtually stripped of any nutrients altogether. This contains almost all the B vitamins your body requires and will take care of that - no need for supplements. Also no refined sugar. These were the main issues and the rest of the time he ate for the other areas in his body he was deficient.
On a side note, I also made up a tea of rosemary, sage and thyme and put it into a spray bottle and sprayed this on his hair after each wash as all these herbs have a hair growing effect. Secondly, I rubbed castor oil into his scalp as castor oil is a well known hair grower. I've also read (but not used) that when you have boiled your potatoes for dinner, save the water and when it cools, use it on your hair and rub into the scalp for a few minutes. Potato water is very good for growing hair.
My son's hair did grow back very quickly as it was completely bald in a patch about 4" by 2" wide so very noticeable. He is now ok but we continue the brown rice on a regular basis to keep up the B vitamins. Good luck with whatever you may use.