Warning:
If eaten, older Stinging Nettle plants must be cooked! Eating uncooked older plants may even cause kidney problems and symptoms of poisoning.
When touched, the hairs of the fresh plant are a skin irritant; the hairs of the dried plant do not seem to have this effect.
References:

The German Commission E confirmed usefulness of Stinging Nettle for:Prevention and treatment for kidney gravel, urinary tract infections, supportive treatment for rheumatism.
“The Herb Book”:
“New Encyclopedia of Herbs and Their Uses”:
lists properties and medicinal uses of Urtica dioica; specifically mentions Stinging Nettle root’s use for prostate enlargement.

Publishing, Zentrum. Herbal Medicine . Zentrum Publishing. Kindle Edition.