Yes, red light therapy produces a short-term and transient production of free radicals in your mitochondria, just like regular sunlight, exercise or a healthy meal does. Maybe you are thinking that it must be harmful, as free radicals linked to increase oxidative stress and inflammation. This in turn we know is associated with disease and aging, but luckily you don't have to worry about red light therapy. The short-term increase in free radicals does not have time to cause any lasting damage to your cells, but rather stimulates an increase in antioxidants. The net effect is therefore rather a protective and anti-inflammatory effect. However, this is a reason not to overuse the red lights. Too long treatment time/effect can theoretically cause the cup to tip over with an excessive production of free radicals, so follow the manufacturer's recommendations. However, it is very difficult to achieve such a treatment effect, so you do not need to worry at all during normal use.