The seller's guarantee on the product - if I have read both threads correctly - is only that it is "fresh" and "genuine."

This is true, so I was wondering as well if OP had a case for a refund/return. However, this was apparently also part of the website text:

With global support and our 110% moneyback guarantee - you simply have nothing to lose!"

This phrasing seems to indicate that you can return for any reason - "nothing to lose." But the OP "lost" on her purchase because either the product is defective and made her break out, or because she is sensitive/allergic to the product.

Still, I'm sure whatever is in the fine print would probably determine the actual limits of the guarantee.