/sci/ - Science & Math

Bacteria cause illness by disrupting the normal functions of our cells. For example, viruses often kill our cells in order to make more copies of themselves, so then symptoms of not having those cells start to pop up.
We can also become ill as a result of our immune system attacking bacteria/viruses. When we get rashes/bumps due to allergies, it's our immune system releasing antihistamines that cause swelling. Additionally, our body temperature will rise in order to help fight infection because certain immune cells function more efficiently at higher temperatures.
Tldr: Bacteria/viruses attack our cells to make us sick, and our immune system makes us feel sick when it fights bacteria/viruses