Eucalyptus, a tropical evergreen endemic to the Australian continent, has been used for centuries as a treatment for skin and upper-respiratory infections. In modern aromatherapy and naturopathy, eucalyptus may be used as a treatment for arthritis, headache, congestion and skin ulcers. Unfortunately, this popular natural remedy is far from risk-free. Like all essential oils, eucalyptus oil may cause unanticipated side effects.
Traditionally, eucalyptus has been used as a remedy for asthma and related complications. However, the University of Maryland Medical Center notes that eucalyptus oil may actually induce an asthma episode in susceptible individuals.
People with allergies to eucalyptus may develop a rash after skin exposure to the oil.
According to the U.S. National Institutes of Health, eucalyptus oil can cause extreme drowsiness, particularly if it is taken by mouth. Skin exposure to eucalyptus may result in fatigue; caution is advised for people taking sedatives.
Infants and young children should never inhale or ingest eucalyptus oil. If it is applied directly to the skin or face of a young child, eucalyptus may lead to wheezing, apnea and asthma-like symptoms. This risk is also present when eucalyptus oil is taken internally.
According to the National Institutes of Health, eucalyptus oil applied to the skin can increase the absorption of Fluorouracil (5-FU), a drug used in cancer treatment. Eucalyptus taken by mouth can interfere with the absorption of drugs that are metabolized by the liver.
Eucalyptus oil should never be taken orally, except under the guidance of a qualified physician. The National Institutes of Health warn that relatively small amounts of eucalyptus oil can cause a fatal overdose. Symptoms of a eucalyptus oil overdose include rapid heartbeat, seizures, abdominal pain, shallow breathing and difficulty swallowing.