Hi John I did not know that! About the cold and heat. I know that dandruff is the shedding of dead skin cells but then why is it that some people suffer from it really badly and others do not? Surely we all shed skin cells? Maybe it is shedding skin cells in very large numbers or a dry scalp that leads to some people being troubled and others not. I would love to know more about this as I get it from time to time, sometimes I think it is because I do not rinse the soap out of my hair thoroughly enough.