system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If a fever, coughing, vomiting or diarrhea are the body’s defenses fighting an infection, why do OTC drugs offer to combat the symptoms? Wouldn't you want the body to do its job?

I understand that deaths related to Spanish Fever were caused by the body's overreaction, but most symptoms of a sickness are the body’s defenses fighting the battle.  Shouldn't they be aided and not suppressed or is it all just marketing and they are really just drugging you with a small dose of DXM?
gpt
The symptoms you list might be *part* of an immune response, but the real work in fighting the infection is being done at the cellular level by your immune system.  Stopping these symptoms does not stop the immune response.

If you have a cold and you stop the runny nose by taking something, the immune system hasn't shut down. It is still actively fighting the virus.  But you just aren't as miserable.

In more extreme cases, like high fevers where the fever does actively help the body, the issue is that the body can push the fever past the point of helpfulness and into a dangerous realm.  We don't know why it does this.  We do know that you can suffer long term consequences from running a very high fever for an extended period of time, so the fever gets treated alongside the illness.

Some symptoms, like vomiting or diarrhea, might help flush out the issue, but again, can cause harm to the body as well (dehydration being the main one here).  They are also not fun symptoms to experience.  But even though these are part of the immune response, they are not the whole thing.  The real work is being done at the cellular level.