Phantom smells are an uncommon type of migraine aura, which is a sensory disturbance just before a migraine happens. Even just one infection can temporarily damage the olfactory system and cause you to smell things like burnt toast. Potential causes include: Sinus infectionĬhronic sinus infections can disturb your olfactory system and cause phantosmia that lasts a long time. Smelling burnt toast can also be a sign of a medical condition, including some serious conditions. Issues that begin in the nose, either in the olfactory nerves in the nose itself or in the olfactory bulb just above the nose, account for 52 to 72 percent of phantom smells. Research suggests that phantom smells can be caused by issues in the nose or in the brain. It’s not fully understood why some people smell things that aren’t there, such as burning toast. Can smelling something burning be a sign of a medical condition?