eli5 does our immune cells try to attack the medication we take while we’re sick? Since medicine is a foreign object. Or does it think of it as a friend who’s there to help.

Question

eli5 does our immune cells try to attack the medication we take while we’re sick? Since medicine is a foreign object. Or does it think of it as a friend who’s there to help.

In: Biology

Answer 1

Most medications are pretty small molecules, so there’s not really a way for the immune system to “attack” them the same way it does with viruses, bacteria, or allergens. For perspective, a single red blood cell contains somewhere in the neighborhood of 200-300 MILLION molecules of hemoglobin, the compound they use to transport oxygen through the body. White blood cells are even larger than red blood cells, so the relatively simple molecular compounds found in most medications are just too small relatively to be noticed by something that’s evolved to identify and attack things like viruses and bacteria.

Some medications do contain allergens like egg proteins or other larger structures that can trigger an immune response in some people. These proteins or other complex molecules are large enough to attract attention, and an allergic reaction is just the immune system going haywire and attacking the substance. Still other medications, vaccines, are designed to elicit an immune response so they can prime the immune system to deal with threats in the future.