I've always ordered my Minox (90% of the times it's been Kirkland brand) on Ebay. Minox has always caused itch and irritation to my scalp since the day I started using it 15 years ago but I was ok with it since it's always done a good job slowing down my hair loss - except in the frontal parts. However, one shipment I received a few months back never caused the usual irritation, stinging and burning. None. I was also losing hair like crazy and my hair was thinning fast. The only thing I could think of was that my scalp must have become resistant to the drug all of a sudden and Minox must have lost its effectiveness after all these years of use. Well, just received my latest shipment of Kirkland a few days ago and now every time I use it I get the usual irritation..... Nothing has changed in my routine. So, I'm sure it has to do with the previous shipment of Minox itself (4 bottles). I can't help but wonder, is it possible that some sellers have some kind of a knockoff Kirkland Minox? How can the lack of any irritation with those 4 bottles out of all the bottles I've bought over the last decade be explained?