The Truth About The Color of Human Blood

There is a universal agreement on the importance of blood towards achieving proper health and function of body organs. However, it seems that there remain questions as to the actual color of blood. Most people argue that it is red. On the other hand, some people are contending that it might not always be read as evident by the blue or green color of the veins through the skin. By looking at the scientific facts, however, people will come to establish that human blood is always red in color.

The science behind the color of blood  

There exists a protein in the human blood which is known as hemoglobin. Hemoglobin has a compound known as heme which is red in color. Other than providing the red color, it serves the essential function of facilitating the transportation of oxygen through the blood circulation system to other parts of the body. Heme contains an atom that binds oxygen to the blood hence improving the blood’s health.  

A crucial factor to consider is that the wavelength of light that chemicals reflect affects how we perceive their color. When hemoglobin is bound to oxygen, it absorbs a light that is blue-green. However, in the human eye, it appears red-orange due to reflection. This explains the reason why blood appears to be cherry red after it is oxygenated. However, without oxygen, human blood will have a deep red color. 

Carbon monoxide in large quantities can affect the process through which blood receives oxygen from the lungs. This is because when this gas is inhaled, it can be bound by heme at a much faster rate than how oxygen is bound. In fact, it has been proved that this bond is stronger compared to oxygen by 200 times. As such, this gas poses a risk to someone’s health as it impacts on how oxygen can be circulated in their body. Without prompt intervention, this can lead to death.  

In such an instance, the blood of such a person will often have a cherry red color. This is because, as stated above, blood which has not been bound with oxygen has that cherry red color. Consequently, the cheeks of a person who has inhaled a lot of carbon monoxide will have a rosy colored appearance.  

Why does blood appear to be blue? 

It is true that at times when you look at your skin, the veins, which have blood, have a somewhat blue appearance. As a result, some people have argued that is appears so because of the absence of oxygen. However, this is incorrect because human blood, regardless of whether it has or lacks oxygen, will always be red in color.  

The blue color that people see can be explained as being an optical illusion. If the vein or artery is deep, then there will appear to be a blue color as a result. This is because the light can only absorb the red wavelength partially thus the reason why one cannot see the red color that blood actually is.  

However, there are a few animals such a horseshoe crab and squid that have blue blood. This does not mean that the health of such animals is compromised. The factor that gives them the distinctively unique blue color is the chemical composition of their blood. These kinds of animals have a chemical known as hemocyanin. The hemocyanin found in these animals has a copper atom which carries oxygen. It is for this reason that one can find the existence of blood in the colors green or blue among other animals. The replacement of hemoglobin with hemocyanin is the cause of the difference in color.  

Regardless, most of the other animals in the world have blood that is red in color. The unique factor about hemoglobin is that there are different types among the various animal species. This has proved to be of investigative importance as scientists use this knowledge to the species of certain blood samples.  

Some people might have also noticed that spilled blood starts to darken after some time. 

This can be explained by looking at the changes that happen to the hemoglobin’s health. It is broken into a compound known as methemoglobin. This is further broken into hemichrome as time goes by. As such, the red color of the blood will continue getting deeper. This scientific information assists forensic teams to identify the duration over which blood has been at a crime scene.

In conclusion, other than knowing the health of one’s blood, people should now be aware that the color of human blood, and that of most animals, is red.