Some tinctures will work well topically. Comfrey is pretty good if it’s the healing property you want. If you’re after its expectorant properties, you’ll be disappointed.
Chemical absorption through the skin is dicey. Many of the important active ingredients in herbs will not absorb through the skin. Internal use will be much more predictable and effective.
Doc
Don't use herbs or combine herbs with medications or use them during lactation or pregnancy without talking with your healthcare provider.