Natural feather and down pillows are generally considered to be the most luxurious pillows available, offering supreme comfort. Furthermore, the higher the ratio of down to feather, the softer and loftier the pillow will feel. This softness is further decided by the quality of the down, as different types (and ages) of bird produce varying sizes of down. Larger down clusters, such as from Hungarian geese, have the ability to trap larger pockets of air, ultimately creating exceedingly soft and lofty pillows.
Unfortunately, because of the allergens inherent in down and feathers, natural pillows (apart from silk filled pillows) aren't suitable for allergy sufferers.
There are many hypoallergenic pillows with synthetic fillings on offer, including pillows filled with either hollowfibre, ball-fibre and microfibre. There are also memory foam pillows which offer a greater degree of support and some middle ground too, like the Silksoft pillows, which are filled with a blend of hypoallergenic silk and polyester fibre.