What is your (diffusing, topical application, or soap making)? What is your budget range ?
Reputable sellers disclose where the plants were grown.
Ensure the bottle comes with a dropper or a built-in plastic "orifice reducer" to maintain seal integrity. Avoiding "Fragrance" Oils
The most critical step is verifying that the oil is 100% pure and therapeutic grade. Check the product listing for the following details:
Because eBay is a marketplace of individual vendors, the seller's reputation is your best safeguard.
If a 15ml bottle of Rose or Sandalwood is priced at $5, it is almost certainly synthetic or heavily diluted, as these oils are extremely expensive to produce.
Authentic oils should list the botanical name (e.g., Lavandula angustifolia for Lavender).
Be wary of terms like "perfume oil," "nature identical," or "scented oil."