Many people can have reactions to down products, but almost exclusively what they are reacting to is not the down protein itself, but allergens contained in unclean down.
Even if the product is new, the down inside could have come from a source that has not successfully cleaned the insulation.
One study looking at allergies to down and feathers involved 269 subjects claiming to have a reaction to down. They were subjected to a down fill in a controlled environment, and 24 subjects had negative reactions. From the fill, dust mites and other allergens found were separated out. From there, 23 of those subjects reacted to the allergens, and only one confirmed a reaction to the pure feather extract.