Eucalyptus

Eucalyptus is a tree. The oil from the tree and leaves is sometimes used in aromatherapy and fragrance. It is also a flavoring used in food in the United States. 

Legal Status:

According to the United States FDA,

• Eucalyptus globulus leaves are included in "Sec. 172.510 Natural flavoring substances and natural substances used in conjunction with flavors." [link] 
• [link] Eucalyptus globulus leaves - FL/ADJ (Substance used in conjunction with flavors), REG (Food additives for which a petition has been filed and a regulation issued.), GMP (In accordance with good manufacturing practices; or sufficient for purpose; or quantity not greater than required), In con­junction w/flavors. 

Health Issues: 

Eucalyptus oil should not be taken by mouth or applied to the skin full-strength. It must be diluted for safety.

According to Medline Plus [link] "Signs of eucalyptus poisoning might include stomach pain and burning, dizziness, muscle weakness, small eye pupils, feelings of suffocation, and some others. Eucalyptus oil can also cause nausea, vomiting, and diarrhea."