The plant is infamous for the burning, itchy welts it raises the moment you brush against it.
Taken as a remedy, that same nettle is used to calm the sneezing and itch of hay fever.

Stinging nettle, Urtica dioica, is the weed everyone knows by feel, the one whose fine hairs inject a cocktail of irritants and leave a burning, bumpy rash when you brush it bare-legged in summer. It grows almost everywhere in the temperate world, and in Germany and across Europe it has been food, fiber, and folk medicine for as long as written records go back.

Cooked or dried, the sting vanishes entirely, and what remains is a genuinely nutritious wild leafy green, rich in iron and minerals, once eaten as a spring tonic after lean winters. German herbal tradition, later formalized in the country's respected herbal monographs, kept it on the shelf for aches, urinary trouble, and seasonal allergies alike.

That last use is the surprising one, and the reason it still turns up in hay-fever remedies on the shelf today. The plant that inflames your own skin on contact is taken, in dried form, to quiet a very different kind of inflammation deep inside the body.

It is a neat little irony, and the proposed mechanism behind it is at least genuinely plausible. Whether it actually does very much in real, everyday practice is a rather more modest story in the end, honestly.

Hay fever is essentially histamine run amok: a harmless speck of drifting pollen triggers a flood of it, and the sneezing, itching, and streaming all follow. Dried nettle appears to interfere with several steps of that cascade at once, blunting histamine's action, calming the mast cells that release it, and damping the inflammatory messengers behind an itchy, streaming, stuffy nose.

The mechanism is plausible, but the human evidence is genuinely thin. A small, much-cited trial found that freeze-dried nettle eased allergic rhinitis slightly more than placebo, and a few later studies hinted it might rival a standard antihistamine, yet all of them were small and methodologically shaky affairs, so the honest verdict is a gentle, hopeful maybe rather than a proven treatment you can count on.

The weed that inflames your skin may quietly calm an inflamed nose.

So it is a reasonable, low-risk thing to try for mild seasonal allergies, and a nutritious green besides, without pretending it matches a modern antihistamine. If your hay fever is severe, or comes with wheezing, chest tightness, or any trouble breathing, that is a job for proper medical treatment and a doctor, not for a soothing cup of nettle tea alone.

The how-to

Try dried or cooked nettle for mild hay fever, and never the fresh stinging plant raw.

Use dried nettle leaf, as a tea or in freeze-dried capsules, or cooked young nettle as a green, since drying and heat destroy the sting completely. The trials used freeze-dried leaf, roughly 300 milligrams a few times a day, so a capsule of that kind matches the research better than a weak tea.
For seasonal allergies, start it before and right through your pollen season rather than waiting for a bad day, and give it a couple of weeks. If you forage it fresh, wear gloves and cook or dry it first, since the raw plant will sting.
At best, expect a modest easing of sneezing, itch, and a runny nose, the kind that takes the edge off rather than the reliable clearing a proper antihistamine gives. It doubles as a nutritious green, so it is fairly low-risk either way.
Nettle is generally safe, but it has mild diuretic effects and may nudge blood pressure and blood sugar, so mention it if you take medication for those or a blood thinner. Avoid concentrated supplements in pregnancy, and if your allergies are severe, or involve wheezing, chest tightness, or trouble breathing, see a doctor rather than relying on a herb.

Tomorrow: Austria and pumpkin seed
the Styrian oilseed with early evidence for calming an overactive, urgent bladder.

See you then.