Check the manufacturer’s website to see if the oil is on the FDA’s GRAS list.

Since oils are concentrated, any pesticides on the original plant are also concentrated. Organic-certified oils are safer for ingestion. A Note on Safety

Ensure the botanical name (e.g., Lavandula angustifolia ) is listed so you know exactly what plant species you are consuming.

Large essential oil companies often have specific lines dedicated to internal use. Young Living has their "Vitality" line.