Bacon is a cut of meat made from pork belly, spices, and additives- none containing gluten. Bacon by itself does not contain gluten. However,  unless specified on the pack, there can be chances of bacon containing gluten because of cross-contamination from facilities processing gluten products.  Additionally, the smoke flavour in some bacon variants comes from barley malt powder, which contains gluten. Therefore, you should thoroughly examine the packaging while buying bacon to ascertain whether it is gluten-free.