Many people can have negative physical reactions to down products thinking they are allergic to down. But the reality is that almost exclusively what they are reacting to is not the down protein itself, but allergens contained in unclean down. Down is a keratin based protein, much like our hair. While it’s possible that one is allergic to such proteins, it is extremely rare.
But even if the product is new, the down inside could have come from a source that has not successfully cleaned the insulation and is thus full of allergens like dust mites and mold. This is another reason it is critical to know exactly where your down comes from.
And keeping your product clean and regularly washed is key to keeping the potential build up of mold and other allergens at bay.