As you can see, there are safety concerns associated with improper use of essential oils. In general, however, essential oils are safe when used externally (not ingested) in low concentrations. For food formulation skin applications, that usually means concentrations no higher than 5%. For inhalation, use intermittent exposure (not more than 15 minutes in an hour). There may not be any safety information on the bottle, but usage guidelines may be posted near sales displays, on company websites, or available through company sales representatives.
If in doubt, always consult a healthcare provider you trust who is knowledgeable about essential oils or willing to investigate with you. There is a great deal of information about essential oils available on the internet, and it may be difficult to critically determine its integrity.