Gather yarrow from a clean area that hasn't been sprayed with chemicals. Double-check that you have identified the yarrow properly before beginning this project.

Roughly chop the yarrow, filling a pint mason jar almost to the top with leaves.

Pour the olive oil or neutral oil of your choice over the yarrow leaves.

Fill a saucepan or slow cooker with 1 inch of water. Carefully place the yarrow- and oil-filled jar on a trivet in a double boiler or in the slow cooker.

Slowly heat the water until it reaches 110 to 120 degrees. Turn off the heat.

Keep the contents of the jar incubating in the warm water. Bring the water back up to temperature periodically over the next 24 to 48 hours, never leaving the heat on for any prolonged amount of time and never allowing the water line to get too low.

When the oil is completely infused, strain out the yarrow leaves.

Pour the infused yarrow oil into a heatproof bowl, place the bowl over a pot of gently simmering water, creating another double boiler.

Stir in the beeswax and let it slowly melt into the oil. Remove from the heat once the beeswax is completely incorporated.

Carefully pour the oil and beeswax combination into prepared salve tins or small jars.

Let the salve cool and set completely before using, around 30 minutes.