Characteristics of the application and its use
A variety of infrared lamps are used in industry e.g. for heating and drying; in medical settings e.g. treatment of sports and muscular injuries (mostly the more penetrating IR-A); and in office and home settings. Recently, infrared warming cabins, or ‘infrared saunas,’ have also become available for home or spa use. Their radiant heat is believed to have therapeutic benefits ranging from treatment of hypertension and congestive cardiac failure, to alleviating chronic pain and fatigue. Supportive scientific evidence for the alleged health benefits is currently limited, however.
There are different types of infrared warming cabins. Two types emit almost solely in the far-infrared (IR-C) region. One type has large, low-temperature wall heaters (surface temperatures about 50 to 70°C) resulting in a uniform, low skin irradiance. The other type comprises ceramic or metallic rods with surface temperatures of 300 to 400°C and metallic reflectors. These irradiate the cabin users from front and back in a much less uniform way. Both types are popular because the cabin air temperatures (around 40°C) are lower than those of traditional saunas (85–90°C). A third type of IR warming cabin has filtered filament lamps that produce emissions in the IR-B range or the IR-A range as well as a small amount of visible light.
IR effects on the body and health implications
When total IR irradiance is very high from sources like incandescent lamps, thermal discomfort of the skin and cornea normally produces an aversion response that limits the exposure time to a few seconds. This aversion response protects the tissues of the skin and eyes from thermal injury. However, other effects of IR exposure are also possible, ranging from whole-body heat stress to elevated cellular temperatures in localized tissues.
In far-infrared warming cabins, skin temperatures are higher than if skin is irradiated with IR-A or IR-B, since IR-C radiation is completely absorbed in the most superficial layers of the skin. Therefore prolonged skin reddening is often seen after IR-C exposure. Chronic, repeated elevation of skin temperature can eventually lead to skin pigment changes and skin damage (erythema ab igne also known as water bottle rash or toasted skin syndrome).Protection
ICNIRP recommends that people at risk from hyperthermia, such as obese people and those with cardiovascular disease, seek medical advice before use of infrared warming cabins. While natural aversion responses (e.g. skin and eye pain) are usually protective, people under the influence of medications, drugs or alcohol who may have diminished pain sensation, should have limited exposure to infrared heating appliances. As a matter of precaution in relation to potential adverse delayed effects of IR, the use of warming cabins and IR lamps should be avoided within 24h of intensive sun exposure or any high intensity UV exposure. Finally, if there is persistent skin reddening lasting more than a day or persistent color changes after exposure to infrared radiation, IR exposure should be ceased and medical advice sought.