Negative ion therapy artificially introduces negative ions through the use of machines called ionizers. Suppose you were near a waterfall or above the tree line in the mountains. The air is charged with negative ions, and you probably feel great. That’s because negative ions are draining. Research has shown that negative ions can reduce blood pressure, improve metabolism and functioning of the central nervous system. Negative ions have also been used very successfully in treatment of allergies, hay fever, and respiratory conditions.