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Stinging nettle (Urtica dioica) is a perennial plant originally native to Europe, North Africa, and parts of Asia but now found worldwide. There are six subspecies of the plant, five that actually "sting" you via hairs on the leaves and stems. These hairs act like miniature hypodermic needles, injecting you with histamine, folic acid, and other substances that cause localized redness and pain.
These properties are believed by some to have a beneficial effect. In early Anglo-Saxon and European folk medicine, stinging nettle was used to treat rheumatism, influenza, and gastrointestinal and urinary tract disorder. In some cases, the plant would be used to make a medicinal tonic; in others, the leaves and stems were applied to the skin to treat muscle or joint pain.
In addition to their medical properties, nettles are used for food, animal feed, and the manufacture of nettle beer popular in England.
Health Benefits
Alternative practitioners believe that stinging nettles can reduce pain and inflammation associated with both infectious and non-infection conditions. Some of the claims are better supported by research than others. Among the conditions stinging nettles are purported to treat are:
- • Muscle and joint pain
- • Eczema
- • Arthritis
- • Gout
- • Anemia
- • Hay fever
- • Urinary tract infections
- • Enlarged prostate
- • Tendonitis
Although research on nettle's health effects is limited, studies suggest that it shows promise in the treatment of the following conditions:
Enlarged Prostate
A number of studies have suggested that nettle may help relieve symptoms of an enlarged prostate gland (also known as benign prostatic hyperplasia, or BPH). The effect is attributed to a plant-based compound known as beta-sitosterol, which is believed to have anti-inflammatory properties.
A 2011 study from India examined the use of a stinging nettle extract in lab rats with medically induced BPH. After 28 days of treatment, the rats experienced a reduction in prostate size similar to the effects of the prostate drug finasteride.
The effect in humans has not been as consistent, in part because the studies usually involved a combination of herbal remedies, including stinging nettle. When investigating beta-sitosterol on its own, the effect on the prostate gland was far more clear.
According to a 2016 review of studies in the Journal of Cancer Science and Therapy, beta-sitosterol is able to reduce prostaglandin levels that directly influence prostate inflammation, reducing the blood flow and size of the gland itself.
Moreover, the effect appeared to be dose-dependent, meaning that larger doses conferred to greater reductions in prostate size. Still, it is unclear how much stinging nettle is needed to deliver a therapeutic dose of beta-sitosterol. Future research will ideally focus on this.
Allergies
A number of studies have suggested that nettle can help alleviate allergies and ease symptoms like sneezing, nasal congestion, and itching.
In 2009 lab study published in Phytotherapy Research, scientists found that nettle was able to reduce allergy symptoms by interfering with two key processes: the histamine response and the degranulation of mast cells.
Histamine is a compound that triggers the body's immune response to an allergen. The stinging nettle extract appears to block histamine from reaching receptors on tissue, reducing the severity of symptoms.
At the same time, stinging nettle prevents an enzyme known as tryptase from reaching mast cells. Under normal circumstances, tryptase causes mast cells to break open (degranulate) and release additional histamine into the bloodstream. Stinging nettle appears to blunt this effect, reducing the amount of histamine circulating in the body.
As with the BPH studies, it is unknown what dose of stinging nettle would be needed to achieve allergy relief.
Osteoarthritis
There is evidence that taking a stinging nettle supplement or applying it to the skin may reduce pain in people with osteoarthritis ("wear-and-tear" arthritis).
It is believed that the very irritants that cause the "sting" of stinging nettles can inhibit enzymes known as cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). These are the same enzymes targeted by nonsteroidal painkillers like Aleve (naproxen), Voltaren (diclofenac), and Celebrex (celecoxib).
According to a 2013 review of studies from the University of Calfornia, Berkeley, stinging nettle possesses potent anti-inflammatory properties that are non-toxic to cells and may be superior to traditional pain relievers.
These conclusions were not entirely supported. A 2013 review in the Cochrane Database of Systematic Reviews pointed out that studies investigating the use of stinging nettle in treating osteoarthritis were of "very low quality."
The researchers further asserted that other herbal remedies appear far more promising, including Arnica extract gel and Capsicum ointments and patches.
High Blood Pressure and Diabetes
Alternative practitioners have long considered stinging nettle to be an effective means of treating hypertension and diabetes. This has been evidenced in part by 2016 study in the Journal of Translational Medicine in which lab rats experienced vasodilation (the relaxing of blood vessels) when injected with a crude stinging nettle extract.
A related study conducted in 2013 reported that a 500-milligram oral dose of stinging nettle taken every eight hours for three weeks was able to lower the blood pressure and blood sugar of people with advanced type 2 diabetes.
Despite the positive findings, the effect was not considered robust enough to be a viable stand-alone option for either hypertension or diabetes.
Rather, it suggests that stinging nettle may be useful for people on antihypertensive or antidiabetes drugs who are still having difficulty controlling their condition.
Possible Side Effects
Stinging nettles are generally considered safe based on their traditional use as food and in folk remedies. Side effects are relatively mild. If taken by mouth, you may experience stomach upset and sweating. If used topically, it is not uncommon to develop skin irritation and rash.
Because of its possible effects on blood pressure and blood sugar, stinging nettle should be avoided if your hypertension or diabetes is well controlled with medications. Even if it isn't, speak with your doctor before using stinging nettle to fully understand the potential risks and benefits.
Stinging nettle also exerts a mild diuretic effect, mainly by irritating the kidneys. Avoid stinging nettle if you have a preexisting kidney condition as the long-term use may increase the risk of kidney damage. Stinging nettle can also amplify the effects of diuretics ("water pills") like Lasix (furosemide) and should be avoided.
This same diuretic effect can reduce the concentration of lithium in the blood, undermining the efficacy of the drug and potentially causing a rebound of depression, bipolar, or schizophrenia symptoms.
Due to the lack of safety research, stinging nettle should not be used in children, pregnant women, or nursing mothers.
Dosage and Preparation
Sold in many health food stores and pharmacies, stinging nettle is available as capsules, tinctures, teas, wax-based salves, and ointment. Freeze-dried preparations of nettle leaf are also available.
There are no guidelines for the appropriate use of stinging needle supplements. Stinging nettle capsules are usually offered in 300-milligram to 900-milligram formulations and are generally considered safe at these doses.
Topical stinging nettle ointment is intended for the short-term treatment of dermatitis and other mild skin conditions. It should not be used as your daily cream as it may cause rash and irritation.
Fresh stinging nettle can also be sourced through specialist grocers. It can be steamed or sautéed in the same way that chard and kale are. Nettle has a spinach-like and slightly minty flavor that many find appealing, particularly when added to vegetable or puréed soups. Some people will finely chop the herb to make a refreshing medicinal tea.
What to Look For
Dietary supplements are largely unregulated in the United States and not subject to rigorous testing or research. To better ensure quality and safety, stick with recognized supplements brands, ideally those that have been independently evaluated by a certifying body like the U.S. Pharmacopeia (USP) or ConsumerLab.
When buying dried nettle, only choose products that have been certified organic under the regulations of the U.S. Department of Agriculture (USDA). This can reduce your risk of exposure to pesticides and other chemical toxins.
Other Questions
Is it safe to forage for wild stinging nettle?
The main challenge when foraging for wild nettle is ensuring that you pick the right plant. Stinging nettle grows from early spring through the summer. The best time to harvest is in the spring when the plans are no taller than a foot and are not yet blossoming. Older plants tend to be tougher and have a bitter taste.
To avoid stings, always bring along a pair of gloves. Avoid picking nettle near roadways or places where pesticides are used.
Stinging nettles are usually recognized by their slight hairy and serrated-edged leaves. Unless you are completely sure what a plant is, do not harvest it. There are smartphone apps today like FlowerChecker, Google Goggles, and PlantSnapp that allow you to photograph a plant and confirm the general species.
How do you prepare fresh stinging nettle?
It is important to blanch or steam the nettles for a few minutes to leach some of the stinging agent (folic acid) from the plant. You can then prepare nettles as would you any other hearty green.
Wrap fresh uncooked nettles in moist paper towels, and store them in a plastic bag in the refrigerator for up to four days. Frozen nettles can keep for up to eight months.
