Near infrared light is of lower frequency than visible light, so it can penetrate matter more easily. UV light barely passes through more than a few layers of s

Near infrared light is of lower frequency than visible light, so it can penetrate matter more easily. UV light barely passes through more than a few layers of skin cells (thereby potentially overloading those cells with a lot of energy, causing DNA damage), while visible light can go millimeters deep, and near infrared can go even deeper. Near infrared can be used to measure bone density. This would not work if bone were fully opaque to IR light.