Bells Menthol Crystals BP are a quick and effective for unblocking noses. The menthol crystals, when added to hot water, release decongesting vapours to clear the airways, and will have you breathing clearly in no time. Bells Menthol Crystals BP are added to hot water to release decongesting vapours clear airways and relieve blocked nose and sinuses. Your congestion will be eased and you will be breathing easy again in no time. All you need to do is add a few crystals to hot (not boiling) water and inhale the vapours.