Is it possible to sweat blood?
Yes it is possible to sweat blood although it is very rare. The condition is called Hematidrosis. Dr Frederick Zugibe explains that there are many blood vessels around out sweat glands, they form a sort of net surrounding the gland. If these vessels are put under great stress the vessels constrict. When they release from this pressure they expand until they rupture. The blood molecules spread out and since they are so close the sweat gland they enter it. When the person sweats the sweat washes the blood our of the sweat gland and onto the skin. The sweat is not only made up of blood, but it has some blood in it, enough to notice that it is red.
Typically high levels of stress on a person will cause the stress on the blood vessels, anxiety and other aliments will not only force these blood vessels to constrict, but they will often make the person sweat. When the stress or anxiety leaves the person, the blood gets into the sweat gland.
It is also said that Jesus sweated blood the night before his crucifixion. Without getting into a debate about God’s existence this can be explained in one of three ways. Either Jesus did not sweat blood, or, Jesus did sweat blood due to high levels of stress (he knew what was coming that would stress anyone out), or, He is the son of God and can do whatever he wants, including sweating blood.
Here’s the medical definition.