Select a mattress depending on spring type, whether it contains natural fillings of wool or cotton, or whether it is certified as Organic. Many mattresses are in multiple categories, for example it is possible to have a pocket sprung mattress with wool and cotton fillings, which is certified as organic. 

Open Coil MattressesOpen Coil Springs Pocket Sprung MattressesPocket Springs Cotton FillingsCotton Fillings Wool FillingsWool Fillings Organic MattressesOrganic