'Allergon+ Plus' is the next step up from 'Allergon', once again the upper surface is a soft cotton terry towelling laminated to a light, breathable, waterproof underside. The difference is that instead of the stretch jersey sides 'Allergon+ Plus' has the waterproof layer running seamlessly up the side of the mattress, over the top and down the other side. Now both sides of your mattress are protected and not just the upper surface. Complete waterproof protection for both sides and the top of your mattress. Machine washable and can be tumble dried.