To understand the effects of negative ions, it’s important to understand the effects that positive ions have on our bodies.
High concentration of positive ions (and a lack of negative ions) is associated with stress due to environment in our daily lives, such as tiredness, cigarette, pesticides, dust... The rug helps to keep a good balance between positive and negative ions. As Rebecca said, I use the rug when my horse is traveling long distances! I had also a Back on track rug (the effects are similar), but it was not as resistant.
It is made with tourmaline, they indicate that the rug: 'release negative ions, Rambo Ionic causes a change in the water in your horse’s body, allowing increased blood flow and circulation in key areas and bringing increased levels of oxygen to muscles to help clear toxins from the body'. I really think it should be efficient! They use the same type of technology for humans. I think I might purchase one for my mare, she is very anxious when traveling and this might help her body not to accumulate too much toxins before the show.