I found this pretty interesting, another explanation of why SOME people lose hair.
CANDIDA AND PARASITES
The same yeast that causes vaginal yeast infections can cause hair loss. This yeast lives in the intestinal tract and is normal in small amounts. Antibiotics, stress, high sugar diets and other factors can cause this yeast to overgrow out of control. Both Candida and Parasites rob the body of nutrition. They live in the intestines and eat our food. Further, they prevent your body from absorbing vitamins, minerals and proteins necessary for hair growth.
The correct parasite and candida elimination program can many times reverse the hair loss problem. However many candida and parasite programs fail. You must make sure that the program you are doing is effective.
For those of you who think I misinterpret everything I read or hear, I'll leave the url to website where I found this.