Why does your body ache when sick?

+54 votes
asked Jun 13, 2015 in Health & Wellness by Regina (650 points)
I got the flu lately and my body aches all over, every muscle and joints. Why does this happen? I heard it is actually quite a common thing to happen. How can falling sick cause my whole body to be that uncomfortable?

3 Answers

+19 votes
answered Jun 23, 2015 by CHARLES (1,050 points)
The theory on why body aches when sick is really interesting. Whenever you fall sick, white blood cells are immediately directed to “repair” your body. Now, the task of white blood cells also includes rebuilding your muscles fibres from daily activity. When the body is down with the flu or so, the immune system will prioritise the white blood cells to get rid of the flu virus. Your muscles and joints receive less maintenance, thus the body will suffer the sore and ache. If you find the pain irritating, take comfort in the fact that your body giving its best to bring you back to shape.
commented Apr 12 by adam_seeliger (100 points)
You're an idiot, no. Completely wrong.

One of the main reasons that your body aches when you are sick, like with a cold, is that your body's immune system is producing plenty of antibodies in addition to the effects of all those viruses replicating in your cells killing them and leaving the area ‘raw’ and exposed.

These antibodies also promote the release of histamine which typically dilates (widens) blood vessel near an infection, this allows for more of the body's defences to get at the infection.  There are histamine receptors in blood vessels that cause them to dilate.

As these chemicals are released into your blood stream they can end up in your muscles or other body parts. Various body systems can have receptors to histamine that can then trigger a pain receptor.

In addition to histamine there are biochemicals called cytokines that are released when the body has an immune response that are also known to trigger a  biochemical pathway that can affect pain receptors.

Histamine and cytokines releases can change the perception of pain receptors in the body making them more sensitive to pain factors.

There are other factors that come into play also such as biochemicals called interleukins that relate to fever conditions and temperature increases, all of which can affect pain receptors in different ways, for example heat receptors.

The overall perception of pains and aches over the whole body can vary from person to person and there may be other combinations of psychological,  physiological or even nutritional factors that may influence this.

A recent hypothesis suggests also that having symptoms of sickness is an evolutionary mechanism to minimise sickness spreading within a group by making a person less mobile or motivated.
+9 votes
answered Jun 17, 2015 by kerena (800 points)
In order to protect the body from the virus, the immune response in the body, the white blood cells in particular, produces a chemical called cytokines. Cytokines help the other cells to respond appropriately to an infection, essentially the cells moderator. While these cytokines do its wonders, it also causes inflammation when in contact with the muscles in a certain way, resulting in pain similar to that of rheumatism or arthritis. So this is why does your body ache when sick. But the ache is temporary at best and will disappear as soon as you are once again free of any virus.
+9 votes
answered Jun 18, 2015 by Kayla (1,090 points)
The reason you fall sick, say from the flu, is your body being invaded by viruses. These viruses kill your cells, leaving the area unprotected, thus contribute to the aching. To counter these invaders, your body will produce tons of antibodies, which promote the release of the chemical histamine that widens the blood vessels attacked. The wider stream allows more of your defence mechanism, i.e. white blood cells among others, to fight in the infected area. Unfortunately, these histamine might end up in your joints and muscles, triggering receptors to histamine that then causes pain.
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