Up until about 15 minutes ago, I believed that dandruff was the result of dried shampoo on the scalp that did not rinse completely. I was in the shower and DW was in the bathroom with the baby because the warm air (coupled with an essential oil dropped onto the bottom of the shower) would help to clear up her nasal passages.
DW mentioned that she was getting dandruff, and I commented on how that was weird because we had never shampooed her. DW was quiet for a very long time, and in the ensuing conversation I learned that dandruff was dried skin shedding from the scalp and not dried shampoo.
She asked me why, then, would one need special shampoo, and I replied because I thought dandrugg shampoo was more soluable in water and therefore left less of a residue on the scalp resulting in less dried shampoo and ergo less dandruff.
A quick peek at Wikipedia confirmed DW's statements (much to my chagrin), and I came straight here.
Oh well, I'll give DW this
one ... she's not right often