Our brain has a pea-sized part called the hypothalamus, which is responsible for maintaining our body temperature (and many other things).
When bacteria or viruses invade the body, one of the immune system’s responses is to produce proteins called pyrogens.
Pyrogens in the blood reach the brain and trigger chemical reactions, which produce a chemical called prostaglandin.
Prostaglandin tricks the hypothalamus into thinking that the body is cooler than it is.
And hypothalamus raises the body temperature above the normal range, causing fever.
So, fever is one of the body’s natural defences against viruses and bacteria that cannot live at higher temperatures.
Paracetamol works on fever by stopping your body from making prostaglandins.
On pain also, it works by stopping the production of prostaglandin.
You see, prostaglandin isn’t just produced in the brain.
It is produced in nearly all cells and is part of the body’s way of dealing with injury and illness.
So, in case of pain (e.g., a dog bite), the immune system sends infection-fighting white blood cells and other chemicals to the impacted site (this sudden arrival causes swelling).
These chemicals trigger reactions at the site to produce prostaglandin, among many other things.
Prostaglandin stimulates the formation of a blood clot and the contraction of the blood vessel to heal the damage and reduce blood loss.
While helpful, the prostaglandin causes pain—a signal to the brain that something is not right.
Paracetamol travels in the blood and travels to reach both the painful spot and your brain, and starts to reduce the feeling of pain by stopping the production of prostaglandin.
