Some essential oils, like eucalyptus and peppermint oil, can help break up mucus. Eucalyptus oil contains eucalyptol, a key ingredient that is used in many over-the-counter (OTC) chest rubs. Peppermint oil contains menthol, an ingredient used in OTC topical rubs to relieve congestion. These oils can help break up and loosen mucus to provide congestion relief.