Smelly farts are normal (so don’t be alarmed). Sometimes it’s due to the type of food you eat. Fiber-rich foods contain sulfur, a natural compound that smells like rotten eggs, that the bacteria in your gut breaks down into gas. Certain types of medication, such as antibiotics, can also affect your gas smell. While rare, smelly farts may be the sign of an infection or disease. These however are usually accompanied by other health concerns.