Forehead Thermometers – Are They Safe?

No-contact forehead thermometers measure the temperature of the body based on the level of thermal radiation being emitted by the skin. They measure temperature from a distance to reduce the transmission of any infection. However given their unreliability are the risks of eye damage really worth it?

Otherwise known as infrared (IR) thermometers, pyrometers, laser thermometers, non-contact thermometers, or temperature guns, these devices are very popular at the moment because they can be used at a distance. Teachers and professionals offering services such as osteopathy are using them to read the body temperature of adults and children to detect fevers before they are admitted to the premises.

The thermometer detects body temperature by measuring the infrared energy being emitted by the skin on the forehead. A lens narrowly focuses the infrared energy coming off the human body on to a detector in the device. The device converts this heat energy into an electrical signal which shows the unit of temperateure on a display screen.


A standard infrared thermometer absorbs infrared but doesn’t emit it, so from that perspective they are safe. The problem with safety comes from laser thermometers, which emit a beam of light to highlight the area of the object being assessed to ensure accuracy. This beam is categorised as a Class II laser which emit visible light below one milliwatt and can be sold as ‘pointers’ used to direct attention to information on smart boards or white boards in lectures. Although they are generally classed as being safe, they can damage the retina if you stare into the beam.

Lasers produce an intense beam of light which can cause laser radiation in the form of thermal tissue damage. The dangers increase the closer you are to the laser the more serious the injury potential.

This laser beam would therefore be extremely harmful if accidentally pointed at the eyes causing severe damage or blinding. The laser beam is a particular issue for children who often move around. In these cases safety goggles are recommended to protect the eyes from accidental damage.

Third Eye / Pineal Gland

If lasers have the potential to damage eye-sight I wonder what the effect will be on the third-eye and its connection to the pineal gland. The third eye sits in the middle of the forehead, above the nose, which is the most popular place for infrared thermometers. The pineal gland is situated directly behind the forehead between the two hemispheres, so I wonder if pointing a laser at the third eye will also cause damage to the pineal gland.

Class II lasers are categorised as being ‘relatively weak’ and ‘normally would not harm an eye unless a person deliberately stared into the beam’. However, if the beam is pointed at the third eye for targeting purposes it may be on the forehead long enough to cause damage, as this is similar to staring into the beam with our eyes.

Scientists have discovered that the pineal gland is a light-sensing organ because it has photoreceptor cells, rods and cones, which strongly resemble those in the retina of the eye.

Dr. Klein has ‘noted that the photoreceptor cells of the retina strongly resemble the cells of the pineal gland and that the pineal cells of sub-mammals (such as fish, frogs and birds) detect light’.

The similarity of the tissue in the pineal gland to the retina raises the question of how it is is affected by laser beams.


The accuracy of the reading depends on the environment in which they are used and the distance from the forehead. They are usually accurate to around +/- 1 or 2 degrees C which is a big difference when you are assessing the presence of a fever.

The UKs National Institue for Health and Care Excellence (NICE) has given forehead thermometers a ‘Do Not Do Recomendation’ warning:

Forehead chemical thermometers are unreliable and should not be used by healthcare professionals.

“These devices are notoriously not accurate and reliable,” Dr. James Lawler, a medical expert at the University of Nebraska’s Global Center for Health Security, told The New York Times. “Some of it is quite frankly for show.”

Crandall’s team found that forehead readings were unreliable indicators of core body temperature.

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