Zinc makes my hair fall out! just taking a modest dose quickly makes my comb and brush much fuller of lost hair each day. I stopped each time I tried it in the last few years due to this effect. But, I may be a case of having to use a much smaller dose than most people, due to possible metallothionein issues.
Some of the metallothionein discussion sites talk about taking zinc in very tiny doses at first if you suspect you are off balance in how your body handles zinc and/or if you suspect problems with your copper levels, such as only taking a portion of one tablet or capsule, and gradually increasing up to a full tablet or capsule over a very slow time period.
Anyway, sometime soon I'll brave the world of zinc again, this time taking tiny amounts only at first, far less than most people would take, to see if I get the hair loss problem again.