hair growing back

Can you explain to me why my hair is growing back? I started out having my chemo treatments (I'm being treated with taxol and carbo) every twenty-one days. This went on for three treatments but because of my low red and white cell count due to the chemo, it was decided that my treatments would be broken up into 3 weekly treatments instead of every three weeks. Between every treatment there was a 1 to 3 week delay with me receiving shots to get my red or white cell count up. I started noticing my hair growing back three weeks ago. Does this mean that the chemo drugs are becoming less effective? Thanks