More on Biotin

The biotin I have been taking is definitely helping my nails; the peeling, chipping parts have mostly grown out and the new nails are much stronger.  My hair is also getting thicker, as my hairdresser noticed.  What pleases me most, though, is that a couple of unpleasant little skin conditions seem to have gone away.  
 

For several years I’ve had small bumpy areas which doctors have identified as seborrheic keratoses; just old age, they said, nothing to be done about it.  Around my elbows I’ve also had bumpy, slightly painful patches (the beginnings of psoriasis?).  Over the course of several weeks both of these have cleared up.  I can’t be sure that the biotin did this and it’s always possible that the placebo effect is operating but whatever the reason, I’m grateful.  If it was in fact the biotin then my question is: were the skin conditions caused by (untreatable) old age or by a treatable nutritional deficiency? 

Update:  Some of the keratoses are still there after all, but smaller than before.  The painful, crusty patches on my elbows are definitely gone.