How can you tell if a piercing is infected or if it's just irritated?

Fever? Pus?: Infection would have signs like redness, warmth, pus drainage, and fever.

Sometimes difficult: It can be a challenge sometimes to tease apart infection vs. Irritation. Pain, warmth and swelling are all signs of possible infection. Redness, flaking, and itching are possible signs of an allergic reaction. See a dermatologist to help determine what may be going on.