Negative ion generators or ionizers have been used for years to help rid closed indoor environments of allergens (such as dust, animal dander, pollen, molds, etc.) floating in the air. The negative ions cause microscopic particles floating in a room – that cause some people to have allergic reactions – to clump together and fall to the floor (or other surfaces) where they can be vacuumed up.

As noted in the book, The Ion Effect, negative ions are effective for allergies, asthma, catarrh, hay fever, eczema, burns, emphysema, and even as a substitute for tranquilizers. It was discovered that negative ions balance serotonin in the body, and this explains why people tend to feel more alert, stable and energized in the presence of negative ions. Dr. Krenger found that bacteria, staphylococci, and fungi growth is halted in the presence of negative ions, which explains the healing side effect. Dr. I. Kombluch mounted experiments at Northeastern Hospital, and at the Frankford Hospital in Philadelphia where he was able to report that 63% of patients suffering from hay fever or bronchial asthma "have experienced partial or total relief" from negative ion therapy.