Inflammation refers to what the body does to attack things that are harming it – toxins, infections, etc.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6272784/

Here's just one! If you google that exact phrase, you'll find many.

Applying something topically does not mean it never reaches your gut – you're less likely to cause a stomach ache but just as likely to irritate an existing gut condition because the medicine traveles through your blood.