Question: what essential oils can you use in a diffuser?
Answer: Lavender. Lavender oil's sedative properties make it a useful oil for calming both emotions and physical concerns such as minor skin injuries, cramping, and sinus congestion. ... 
Tea tree. The benefits of tea tree oil far outweigh its strong medicinal scent. ... 
Peppermint. ... 
Orange. ... 
Lemon.