Asthma strikes more and more people. Bad air quality, indoor or outdoor, is often a triggering or aggravating factor of asthma. An air purifier can help get some relief, and have good nights.
Among air pollutants having an influence on asthma, particles and ozone play an important role.
Studies have shown that the level of hospitalizations for asthma increases when levels of particulate matter in the air rise. For example, an epidemiological study for the city of Phoenix (US, Arizona) quantified a 13% increase of asthma risk among children ages 5-13, for a PM10 daily mean increase of 36 µg/m3 (https://www.atmos-chem-phys.net/12/2479/2012/acp-12-2479-2012.pdf). This is to be compared with the recommended maximum PM10 daily exposure by the World Health Organization: 50 µg/m3 - a value which is often exceeded in many urban areas around the globe.
Natural logarithm of the odds ratio (log odds) of asthma incidents versus categories of Dailymean PM10 concentrations (µg/m3). Source https://www.atmos-chem-phys.net/12/2479/2012/acp-12-2479-2012.pdf
Ozone is a powerful oxydant, very toxic even at small concentrations. Significant pulmonary function reduction have been observed on athletes exposed to as low as 0.2 ppm concentration, for as short a duration as 1 hour. Ozone can cause damages to lungs, loins, the brain and the eyes. Several scientific works even consider that ozone can be toxic from the first molecule, which means that there is no threshold under which anyone can be safe. Since a few years, international standards forbid to sell air purifier products generating more than 50 ppb (0.05 ppm) of ozone.
Negative ions efficiently reduce particles pollution.
Fifty years ago, a French scientist, Professor Jean Bricard, awarded by the French Academy of Sciences, and called the Father of Aerosol Science in France, established a law correlating aerosols (particles) density in the atmosphere with negative ions density in the same air. The more negative ions, the less particles in the air.
Since then, engineers have tried to develop ways to generate negative ions in the air, as a way to purify it. Several scientific studies have quantified the impact of negative ions on indoor air purification. You will find some of them on Teqoya website: https://www.teqoya.ch/en/research-review-health-benefits-of-negative-ions/.
Physical mechanisms explaining the action of negative air ions on aerosols (particles in the air) are now well-known, and air ionization can be used as an efficient solution for air cleaning. You can have a look to https://www.teqoya.ch/en/ionisation-negative-ions/ for explanations.
Negative oxygen ions have a biological action that improves the oxygen uptake by the body.
It has been reported by biological studies that the oxygen intake by the cells increases when the air is charged with negative oxygen ions. However we must indicate that, up to now, such studies have been run mainly with animal cells. You will find an example here: https://link.springer.com/article/10.1007%2FBF01553139. However, physiological quantitative tests on men have been performed, confirming that negative air ions are biologically active: http://europepmc.org/abstract/MED/8064146.
This improved oxygenation of the blood may help compensate some of the asthma symptoms and, as such, be a relief to asthma-stricken children, and adults.
Finally, negative ions beneficial effects on asthma has been reported by some quantitative medical studies.
You will find examples of such studies on Teqoya website at : https://www.teqoya.ch/en/research-review-health-benefits-of-negative-ions/.