A worrying message widely shared on Facebook warns that infrared thermometers may be “causing potential health issues by aiming an infrared ray to the pineal gland”.
The message says the thermometers, commonly used to measure temperature when screening for Covid-19, “target the pineal gland, which is located directly in the centre of the forehead, with an infrared ray”.
The claim has also appeared on YouTube and on blogs promoting anti-vaccine and other conspiracy theories. Its origin is not clear. That the message’s anonymous author is only identified as “an Australian nurse” is early cause for suspicion.
But is this how the thermometers work? And do they damage the pineal gland?
Emission impossible
The message claims infrared thermometers release a beam of infrared light, a type of light not visible to people but that can be felt as heat, to measure a person’s temperature. But the thermometers only detect infrared radiation – they don’t, and can’t, emit it.
This has been noted by several fact-checking organisations that have been debunking increasingly dramatic versions of the hoax since it was first picked up by a Lithuanian fact-checking site in May 2020.
People radiate some body heat in the form of infrared light. Infrared thermometers detect this and determine how hot a person’s body is according to the intensity of the light or radiation.
A video of a badminton player taken with a camera that can detect infrared light shows how, as she exercises and her body heats up, she radiates more in the infrared.
And the pineal gland is not “located directly in the centre of the forehead”. It is located deeper in the skull.
Not all thermometers are created equal
The Mayo Clinic, a US medical non-profit, explains that infrared thermometers are used because they are non-invasive and easy to use, although they do have drawbacks.
A meta-study of 37 different assessments of infrared thermometers found they were not accurate enough to replace more invasive rectal thermometers. And some experts have voiced concerns that infrared thermometers may fail to detect many Covid-19 cases.
But the same study advised that infrared thermometers could effectively replace other, less invasive thermometers.
The Facebook message also says that pointing an infrared thermometer at the wrist instead of the forehead gives a more accurate temperature reading. But this is not true. The US Food and Drug Administration recommends pointing infrared thermometers directly at the forehead for an accurate reading.
Experts from the Meedan Digital Health Lab, a journalism project aimed at addressing health misinformation, say no digital thermometers, including infrared ones, have any effects on health.
“Digital thermometers do not damage your brain in any way,” they write. The messages on social media warning people about the dangers of infrared thermometers are inaccurate and fear-mongering.
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