Infrared waves are dangerous because they can cause burns, skin irritation, dehydration, low blood pressure and eye damage. A form of heat radiation, infrared waves are most dangerous at high levels.
Infrared waves have a wavelength lower than the threshold of visibility on the electromagnetic spectrum, so we cannot see them. However, we can feel them as heat.
Welders have a risk of eye damage through infrared waves involved in the process of welding. If the eye is exposed to intense infrared waves, it can cause blindness. Goggles can be worn to prevent this. Infrared waves are used in therapy for muscle pain, but if the waves are too strong, they can cause skin burns. Infrared radiation can sometimes cause low blood pressure in the elderly. Lastly, excessive infrared radiation exposure can cause dehydration as the body loses water because of the heat.
Rather than being regarded as dangerous, though, infrared waves are more often than not considered useful. There are five subdivisions of infrared waves. The shortest wavelength of infrared waves is used in short-range communication such as remote controls and mobile phones, and it produces so little heat that we cannot feel it. The next subdivision is "short wavelength infrared," used in longer-range communications. "Mid-wavelength infrared" is used in missile guidance, and "long wavelength infrared" is useful for thermal imaging. Thermal imaging is important in the medical field for diagnostic purposes, detecting levels of infrared radiation of the body. "Far infrared" has the longest wavelength and is used to detect galaxies and stars emitting infrared radiation.