Nettle Leaves for Salve-Only younger leaves?

This is the first year that I will try to make anything with Stinging Nettle.  I found out that since our plants were budding already that they are too old to use for cooking, infusions, etc. (internal use).  I was wondering if the plant leaves can still be used to make salve that you use externally only, or is it still better to wait for the next young leaves to use?  Will the older leaves still be risky (health-wise) even applied externally (given our skin is our largest organ)?  Would the leaves simply be less beneficial in a salve (given that the plant's energy is now being focused on the flowers)?  Thanks for any insight.  

According to this site, http://www.wolfcollege.com/stinging-nettle-harvesting-processing-and-recipes/
 internally you can use stinging nettle up until bud formation. For topical medicines, as long as the plant is green and alive, you can use it.

Stinging Nettle is a wonderful food, incredibly nutritious.  Make soup with the early spring leaves, or dry it to make an infusion (1 oz dried nettle in a quart jar, fill to the top with boiling water, put a lid on it, sit for 4hr-overnight, drink over ice)

I would rather make a salve with calendula, comfrey, or plantain instead because those are plants that are nourishing to the skin.