Carpenter ants will bite to defend their nests, if threatened. Because carpenter ants, like some other ants build nests in hollowed out trees and woodpiles, humans sometimes accidentally encounter defensive carpenter ants, that use their woodcutting mandibles to bite and fend off intruders, when provoked.

Equipped with strong mandibles, bites by this relatively large ant species may break the skin, leaving sizable bite marks. Carpenter ant bites resemble pea-sized red blemishes. For sensitive individuals, bites might swell, becoming inflamed and may take just over a week to disappear completely. Carpenter ant bites feel like sharp pinches, because they are and may be quite painful. The same acid found in bee stings, formic acid, might be injected into the wound during a bite, making the pain worse. The bite pain, felt immediately, is accompanied by a prolonged burning sensation if formic acid is involved. The good news is that although painful, carpenter ant bites do not contain venom or transmit diseases, therefore not posing ant health threats to humans.

Immediately after experiencing carpenter ant bites, clean wounds with soap and warm water. Apply antibiotic ointment to a wound if the skin is broken. Bandage the wound after cleaning if desired. Avoid scratching wounds that may begin to itch for several days. Applying ice packs to wounds can help reduce itching.