Stinging Nettle is quite a nasty plant to touch, but oral ingestion of pills without spikes results in a moderately potent anti-inflammatory that can reduce the sniffles. Does not boost testosterone despite being claims to, although it can help Benign Prostatic Hyperplasia and urine abnormalities.
120mg of Stinging Nettle (root) taken three times a day (totalling 360mg) is associated with benefit in Benign Prostate Hyperplasia.
For allergies, the studied dosage is 300 mg twice a day of freeze-dried nettle leaf. The evidence is much better for nettle root and prostatic enlargement than for nettle leaf and allergies.