There are times when you need to buckle down and really start paying attention if you're dealing with allergy symptoms but not sure why. Take notes on any symptoms you notice and mark the date/time they began. As soon as you have some more information to hand, speak to your doctor about potential triggers. If you have been sleeping on the same mattress for 7 years or more, even if you aren't allergic to something in it, you might want to consider a new one. It's a good sign it's time for a new mattress if it's sagging or if it's no longer comfortable.