I purchased a lovely pair of black gloss original hunter boots, which when they arrived were a beautiful deep glossy black. However they were the wrong size, so I reordered the size down, which when arrived were completely covered in white bloom, and definitely not glossy or black.
I did a google search and tried all the suggestions - warm soapy water (does nothing!), olive oil (manages to disguise the blooming momentarily, but not remove it) and all sorts of household cleansers, none of which worked.
I decided to instead research rubber blooming which came up with a number of solutions - one being to find a solvent, or something that you would use to clean your car tyres (Armour All). I had no Armour All, and the closest thing I could find to a solvent was a bottle of Manicure Brush Cleaner. It worked like a dream! Completely removed the bloom, and the boots are even more black & glossy than my first pair!
I realise that this product is quite strong, and the Hunter website says specifically not to use any solvent products, but I'd much prefer risking that than having boots I am not happy wearing.