Cosmetics can not only change the skin infrared temperature measurement value, the error may also be large.

Right now, the new coronavirus is ravaging the world, and non-contact infrared thermometers are widely available at the entrances of various public places. As long as you go out, you will inevitably be measured several times a day. Although today's infrared temperature measurement technology is changing rapidly, this long-range non-contact infrared thermometer still has many defects. A recent Korean study suggested that the widely used cosmetics (including some skin care products, the same below) were unexpected unexpected interferers that could easily change the infrared temperature measurement of the skin, and the error may be large, sometimes enough Mask the abnormal body temperature of a fever patient.

A device for detecting the temperature of passengers at an airport in South Korea

The research was carried out by a team led by Steve Granick, a materials scientist at the Korea Institute of Basic Sciences (IBS). The results were published on the preprint website MedRxiv recently. According to Dr. Dong Ruoyu, who is also one of the authors of the article who personally participated in the experiment, they first selected ten common cosmetics such as whitening cream, face cream, high-gloss powder, sunscreen lotion, sunscreen, foundation, lotion, toner, gel cream, mask / Skin care products, then apply the same on your face every time (not full), and then use an advanced research-grade infrared camera to measure the temperature change of the skin covered by cosmetics.

Ten kinds of cosmetics used in the experiment

The infrared temperature measuring camera FLIR A8303sc used in this experiment has an accuracy of 0.02℃

In order to ensure the accuracy of the measurement, they do not measure the absolute value of the face temperature, but measure the temperature change of the painted area compared to the unpainted area. Considering that the temperature changes caused by physical activity should be avoided as much as possible, Dr. Dong must be sitting there for long-lasting cosmetics, even for more than an hour.

Dr. Dong applied cosmetics and temperature measurement process

The labor was not in vain, and the experiment yielded an unexpected result: the ten cosmetics they tested reduced the temperature of the face to varying degrees. Among them, two types of cosmetics have the most obvious cooling effect. The first category is cosmetics such as creams, masks, lotions, etc. They can cool down the skin by more than 4 ° C within 5-10 minutes after application, but this cooling effect will gradually disappear soon afterwards. The second category is cosmetics with particulate matter, such as whitening cream and high-gloss powder. In addition to their good cooling effect, the cooling duration can even be as long as 20 minutes or more. Although the cooling effect of the rest of the cosmetics is not so amazing, it can usually reduce the temperature by more than 1 ° C within a few minutes (see the figure below for details).

Temperature measurement results, left: experimental temperature measurement photos, cosmetics are applied to the right side of the experimental staff's forehead, the temperature measurement of this part shows green (lower temperature). Right: Cooling curves of several cosmetics with obvious cooling effect, including 6: foundation; 7: emulsion; 8: toner; 9: gel cream.

The paper analyzes that the reason why cosmetics such as facial masks and toners are so effective is that these cosmetics have high water content and the liquid evaporates and absorbs heat, which causes the actual temperature of the skin surface to decrease. For cream cosmetics, if a sufficient amount is applied and a thermal insulation film is formed on the skin surface, the temperature detected by the infrared camera will be lower than the actual temperature of the skin. For cosmetics such as high-gloss powders containing reflective solid particles, infrared cameras actually do not directly detect the surface temperature of objects, but detect the strength of infrared signals emitted by objects. When reflective particles are adsorbed on the skin surface, The infrared emissivity will decrease, the signal detected by the infrared camera will become weaker, the measured temperature will become lower, and the cooling time under this action mechanism will be longer.

At the end of the article, the authors frankly introduced some deficiencies and limitations in the work. For example, the choice of cosmetic brand (and ingredients), the way of application (and dosage) may affect the experimental results. In addition, we also need to consider that some test conditions in the experiment and the actual use environment may still differ. For example, in a well-ventilated public place and in a closed laboratory, the temperature measured by the infrared thermometer may be different depending on the environment. In addition, the skin condition varies from person to person, and the degree of absorption of the same cosmetics may also cause a difference in the cooling effect.

However, the author believes that these factors will not fundamentally overturn the results of this study, so the conclusion that cosmetics can temporarily lower the skin temperature should be credible. In addition, the article also mentioned that because general cosmetics are not applied to the ears, it is relatively reliable to measure the ear temperature.

In view of the current global use of non-contact forehead temperature guns to measure the temperature of people passing by, or the use of remote infrared temperature measurement devices in public places to screen virus-infected people, the results of this study are worthy of causing public health authorities, governments and The public's attention.

Source: https://www.kepuchina.cn/wiki/faq/202004/t20200407_1220486.shtml