I've never used a pure essential oil before. How exactly do I use this tea tree oil safely, and what should I mix it with?

Since this is a pure, undiluted essential oil, it's too potent to apply directly to your skin. To use it safely, you'll need to mix a few drops into a larger amount of a neutral base, which is often called a carrier oil. For a massage or body oil, add 4–6 drops of tea tree oil to about 30 ml of a carrier oil like jojoba, sweet almond, or fractionated coconut oil. For adding to a bath, mix 5–8 drops into a tablespoon of a dispersant like full-fat milk or a bath salt base before adding to the water; this helps it mix properly and reduces the risk of skin irritation from the undiluted oil touching you directly.

For scalp or facial use, where skin can be more sensitive, dilution should be higher. A common starting point is adding just 1–2 drops of tea tree oil to 10 ml of your chosen carrier oil. The characteristic sharp, clarifying aroma and feel of tea tree come from its concentrated natural compounds, so a little goes a long way in any mixture. Always do a patch test by applying a small amount of your diluted blend to the inside of your forearm, waiting 24 hours to check for any reaction, before using it more widely.