This long, skinny plant caused red bumps on my son's knee within minutes. Is it poisonous?

Question

Out for a run with my son and this plant brushed up against his knee. Within seconds it made small red spots and within minutes the spots turned to small bumps.

What plant is this, and more importantly is it poisonous? Any advice?

We live in Minnesota and it's currently September.

Out of curiosity: in which country do you live? For me as a German it's hard to imagine that someone doesn't know stinging nettles. They're ubiquitous here, and everybody knows and avoids them. — Ralf Kleberhoff, Sep 15 '21 at 07:20
I can't believe how quickly I got an answer and how much this blew up...all within 12 hours. This community is a treasure! And for those asking, I'm an ignorant homebody suburbanite from Minnesota :) — LCIII, Sep 15 '21 at 17:14
Comments are not for extended discussion; this conversation has been moved to chat. — Willeke, Sep 17 '21 at 19:26

score 59 · Accepted Answer · edited Sep 15 '21 at 18:16

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Yes, it is a stinging nettle, they can cause itchy rashes and general irritaion but should subside within 24 hours.

They are actually eaten after being cooked some places, and are widely used to treat a variety of ailments as an herbal medicine, such as hay fever and osteoarthritis.

Medicinal properties

The leaves and young stems of this herbaceous plant are fitted with stinging hairs tipped with formic acid and other irritants. If touched, these needle-like hairs inject the stinging acid into the skin, triggering a burning, tingling sensation and an itchy rash. Thankfully the symptoms usually do not persist longer than 24 hours. Interestingly, the cooked plant is safe to eat and is popular is some places as a vegetable.

Source

They are irritating but nothing to be too concerned with assuming there is no abnormal reaction or allergy.

More information on the plant and its varieties can be seen here: Urtica Dioica information

edited Sep 15 '21 at 18:16

Don Branson

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answered Sep 14 '21 at 22:50

Nate W

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After a bath the bumps have gone down. Woo hoo! – LCIII Sep 14 '21 at 23:05
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Glad to hear it, the worst of it should be passed then. – Nate W Sep 14 '21 at 23:07
That patch of skin might feel a bit irritated to the touch even after the bumps go, sometimes even for a few days. It's annoying, but it's not harmful and it'll pass. The nettle is a very common weed where I live, so I get stung often when working in the garden. – Dronir Sep 15 '21 at 07:21
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When we were children, adults always told us that getting stinged by tham was good against reumatism. – Vladimir F Героям слава Sep 15 '21 at 07:27
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There may be a dock leaf nearby. Pick a large leaf and rub it gently on the sting. That's the folklore, anyway. See Why do nettles sting? And do dock leaves really help? – Weather Vane Sep 15 '21 at 08:08
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24 hours is rather an overstatement. The burning usually subsides within minutes for most people. At least with those here in Germany. – Philipp Sep 15 '21 at 08:32
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I’ve gotten stung by them all my life. It actually gets less painful over time. – Michael Sep 15 '21 at 08:51
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They're generally mildly painful in spring; stronger toward the end of summer and into autumn. – TRiG Sep 15 '21 at 09:23
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@Philipp: Yes it usually goes down after a few minutes, but I've occasionally had stings that lasted much longer... – psmears Sep 15 '21 at 10:13
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As with scrapes and bruises, what might be an inconvenience for an adult might seem to be a major incident for a child. – Weather Vane Sep 15 '21 at 10:30
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@VladimirF a common folk remedy, with only a little evidence. But people do deliberately sting themselves without harm. My legs and hands get stung often enough cycling off road (even occasionally on road) when avoiding them isn't an option. They can sting through thin clothing – Chris H Sep 15 '21 at 11:03
... I remembered the name urtication – Chris H Sep 15 '21 at 11:54
I've heard that the liquid from ferns helps. – Davidw Sep 15 '21 at 14:58

score 26 · Answer 2 · answered Sep 15 '21 at 13:42

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Stinging nettle. It's so common on almost any open patch of ground in the more temperate parts of Europe that it seems weird to see this question: I'd expect every child here to have frequent encounters with them.

Their leaves sting and inject formic acid, and the bristles on the stems are quite more thorough with the same. Brushing against them tends to deliver warning bumps (more white than red though) that wear off in about an hour. Falling into them tends to trigger the nastier bristles on the stems, usually good for several hours.

The stinging and burning action is quite basic chemistry, so I don't think that the reactions between people with allergies and others will significantly differ. Skin toughness may make a difference.

The principal remedy is stoicism and ignoring the burn until it subsides.

answered Sep 15 '21 at 13:42

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For me, and I assume many more, a remedy was taught while we were quite small. One leaf of one of several plants to be rubbed onto the sore spot. (Many plants work, even soft grass.) – Willeke Sep 15 '21 at 16:41
@Willeke Ahh yes, the remedy here is to rub with the Dock Leaf, which always appear to grow nearby. (A natural counterbalance in the soil, or something?) – PCARR Sep 15 '21 at 18:11
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If you don’t know what a common plant like stinging nettle is you probably shouldn't rub another plant on your skin, as you might choose something worse… – Stefan Sep 15 '21 at 19:57
@PCARR it's actually unclear that dock leaves do anything beyond placebo - https://www.discoverwildlife.com/plant-facts/do-dock-leaves-really-soothe-nettle-stings/... but I agree, it definitely does seem to help! – Tim Sep 15 '21 at 19:58
In my neighborhood the common remedy was mud from the bank of a stream, applied directly to the sting. Probably also placebo, but we thought it felt better. – Wayne Conrad Sep 15 '21 at 22:49
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since the "cure" is "wait it out", placebos are perfect in this case. Telling a kid "you have to deal with it until it goes away on its own" will result in a MUCH unhappier child than "here, put this (harmless! and easy to recognize for the kid, so it doesn't use something bad in the future!) stuff on it" – Syndic Sep 16 '21 at 08:42
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For us (as kids), the cure was the sap(?) of Lamium_album - since it looks a lot like stinging nettle minus the stinging parts, it made perfect sense to us as kids. Plus, we liked the plant already because you can suck sweet nectar out of its flowers. – Syndic Sep 16 '21 at 08:45
@Tim: https://en.wikipedia.org/wiki/Plantago_major might help too, but I don't know how much % of its effect is due to placebo. – Eric Duminil Sep 16 '21 at 10:00
Smear a little butter (or margerine) on the sore spots. Takes away the stinging almost immediately. Proper butter from cows milk. The soy-based or other purely plant-based butter imitations don't work. – Tonny Sep 16 '21 at 15:30

score 2 · Answer 3 · answered Sep 16 '21 at 23:29

As others have already mentioned, it's a stinging nettle.

The hairs that deliver the sting into your skin are actually not very strong, and they mostly reside on the underside of the leaves. There's a saying "if you grasp the nettle firmly, it will not sting you", and this comes from the fact that if you choose to harvest a nettle, by grasping it in a smooth motion to use the topside of the leaves to protect you as you grip the stem to pull up the plant, you can avoid being stung.

There's herbal extracts you can get that include nettle, I've also consumed it in a tea (and it had quite a unique, yet pleasant taste). I have heard of it being used as a flavour ingredient in soup also.

The stings do indeed ease after about a day, but they can be quite painful and one can cause more pain overall by scratching them as they are intensely itchy. In my personal experience, once stung, it is important to ensure that you've removed all the stinging hairs from yourself and your clothes or they will continue to sting. As a child I was always advised to apply wet mud to the stings and let it dry in order to ease the pain and itching - it did seem to work.

In my book harvesting nettle is done by pinching the top 5cm of the stem. Not uprooting the whole plant as the lower leaves are old and not tasty (also why kill it). — Vorac, Sep 21 '21 at 14:46
@Vorac When I was a kid we weren't harvesting them, we were trying to remove them to grow vegetables. — James D, Sep 21 '21 at 22:20

This long, skinny plant caused red bumps on my son's knee within minutes. Is it poisonous?

3 Answers3