The second method of nasal irrigation is to introduce some form of positive pressure to the water introduced into the sinuses and nasal cavities in order to provide a more complete rinsing without resorting to special techniques, such as holding the head to one side (which is usually difficult with a neck condition). Some products available from pharmacist supply retailers are essentially bottles made of flexible plastic with special tips to fit the nostril. These bottles, when filled with warm salt water solution, can be squeezed to exert positive pressure of the water flowing through the sinuses while the mouth is kept open at all times in order to breathe and prevent snorting the liquid down the throat.