People commonly say that a woman is glowing while pregnant or when they are looking their best. Another common compliment is that someone looks bright, or that they have a light to them.

According to a study published in the Journal of Physical Chemistry Letters, these compliments might be closer to reality than most people would think. This is because humans actually do glow, though the light is far too dim for our eyes to pick up on it. The fact that humans are at least slightly bioluminescent was first shown in 2009, but the new study helps to explain how and why.

The authors of the 2009 study wrote:

“The human body literally glimmers. The intensity of the light emitted by the body is 1000 times lower than the sensitivity of our naked eyes.”

The amount that a person glows will change throughout the day, likely associated with the circadian rhythm, which also governs our sleep. The study also showed that our faces glow the most, though the whole body does as well.

To prove this, researchers used an imaging system that are able to detect biological ultraweak photo emission (UPE). In addition to showing that humans glow, the study also showed that all life has a weak glow to it, including plants and animals. The level of the glow changes based on a variety of stimuli, and soon after the end of a life, that light goes out.

To learn more about how animals (and now humans) glow, check out this informative video:

This isn’t just interesting, but it can actually be helpful. The researchers found that when an umbrella tree was cut, the glow increased as the tree moved to repair itself. This, they propose, could be useful information for monitoring the health of forests. In theory, something similar could be done for humans. If doctors could detect the changing glow of a patient, they might be able to identify the location of diseases and catch them earlier than is currently possible.

All this is interesting, but one might wonder how and why we glow. Well, if you can look back to 9th grade science class, it is because of mitochondria (yes, the powerhouse of the cell). It releases small amounts of reactive oxygen species (ROS) while producing energy. Those ROS react with the other molecules in the body, which emit biophotons, causing the body to glow and glitter.

While science is still some way off from being able to easily monitor the glow that a person is giving off, this research is fascinating and will hopefully someday develop into a powerful medical tool.

Telling someone they are glowing is more accurate than you think.

If you found that story interesting, learn more about why people often wake up around 3 AM and keep doing it for life.