Stinging Nettle Root Side Effects and Who Should Avoid It: What the Research Shows
By Real Herbs Editorial Team · Published October 2026 · Updated October 2026 · 9 min read
Key takeaway: In the human trials of nettle root, adverse events were reported as few and were not more frequent than with placebo. The European Medicines Agency (EMA) lists stomach and bowel complaints and allergic skin reactions as the possible reactions, and says how often they occur is not known. Check with a doctor or pharmacist first if you are allergic to nettle, are pregnant or breastfeeding, are under 18, take regular medicines, or have urinary symptoms that no one has checked yet. Most trial participants were men over 60, and none of the studies cited here tested this exact product.
Stinging nettle root (Urtica dioica) is sold as capsules, tablets, liquid extracts and cut root for tea. This guide sets out what clinical trials and EMA reports say about side effects, who should check with a health professional before taking it, and when to stop and seek advice.
Disclosure: Real Herbs sells a stinging nettle root extract. We report the safety information as it was published.
Reported side effects
The EMA’s herbal committee reviewed the safety data for nettle root in a 2025 assessment report. It lists two groups of possible reactions, both with a frequency listed as not known ([1]).
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| Type of reaction | Reactions listed | Frequency (EMA) |
|---|---|---|
| Stomach and bowel | Nausea, heartburn, diarrhoea, constipation, feeling of fullness, gas | Not known |
| Skin and allergy | Itching, rash, hives (urticaria) | Not known |
Regulatory report The report also notes that more than 17,000 patients were tested for safety in clinical trials, that no cases were found in the EU pharmacovigilance database (EudraVigilance) when it was searched in 2021, and that no case of overdose has been reported ([1]). It draws on older studies as well: an open study of 5,492 men over 3 to 4 months listed 54 gastric complaints, 12 cases of diarrhoea and 22 other complaints, and a 3-month double-blind study of 41 men listed one case of dizziness, which the report says may relate to the ethanol in the preparation ([1]).
A review of the nettle root literature describes the risk of adverse events during treatment as very low ([2], PMID 17509841).
Tolerability in clinical trials
These are the safety findings stated in the published abstracts or in the EMA report. Several of the studies tested a fixed combination of nettle root and saw palmetto, which is marked in the table.
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| Trial | Product | Length and size | Safety finding reported |
|---|---|---|---|
| Schneider 2004 | Nettle root dry extract, 459 mg (Bazoton uno) | 12 months, 246 men | Fewer adverse events than with placebo (29 against 38), and fewer urinary infections and similar events (3 against 10) ([3], PMID 15045190) |
| Karami 2020 | Nettle root extract tablets, 450 mg a day | 12 weeks, 60 men | No side effects were seen ([4], PMID 32981268) |
| Safarinejad 2005 | Nettle root extract | 620 men, followed for up to 18 months | The EMA report states that no side effects were identified ([1]) |
| Lopatkin 2005 | Combination: saw palmetto 160 mg + nettle root 120 mg | 24 weeks, 257 men | Tolerability comparable to placebo ([5], PMID 15928959) |
| Lopatkin 2007 (follow-up) | Same combination | Up to 96 weeks, 219 men followed | One adverse event per 1,181 treatment days; in one event only could a link to the product not be excluded ([6], PMID 18038253) |
| Sökeland 1997 | Same combination, compared with finasteride | 48 weeks, 543 men | Fewer adverse events than with finasteride, including fewer cases of reduced ejaculate volume, erectile dysfunction and headache ([7], PMID 9340898) |
Human trial Taken together, the nettle-alone trials found adverse events no more common than with placebo. Most participants in the trials were men over 60, and the EMA report notes that BPH is a condition of older men ([1]). The studies also used different extracts from one another, so their safety findings describe those extracts and not nettle root as a whole.
Who should check with a doctor first
The sources point to a small number of groups who should speak to a doctor or pharmacist before taking nettle root. The table sets out what each source says and a practical next step.
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| Situation | What the sources say | Suggested step |
|---|---|---|
| Allergy to nettle | The only contraindication the EMA lists is hypersensitivity to the active substance ([1]) | Do not take it. If you have reacted to nettle before, tell your doctor or pharmacist. |
| Pregnant or breastfeeding | The EMA report says there is no information on reproductive and developmental toxicity, so use during pregnancy and breastfeeding is not recommended ([1]) | Do not take it unless your doctor advises it. |
| Under 18 | The EMA lists no relevant use in children and adolescents; BPH is a condition of older men ([8]; [1]) | Not intended for under 18s. |
| Urinary symptoms that have not been checked | BPH and prostate cancer can cause the same symptoms ([9]) | See a doctor first, and keep up regular prostate checks. |
| Taking regular medicines | The EMA reports no interactions, but states that specific interaction data are not available ([1]). The trials cited here did not test nettle root with other drugs. | Ask your doctor or pharmacist first. See nettle root and medicines. |
| Taking BPH medicines | None of the trials cited here tested nettle root alone together with alpha-blockers or finasteride | Ask the prescriber before combining them. |
| A sensitive stomach | Stomach and bowel complaints are among the reactions the EMA lists ([1]) | Take it with food, as the Real Herbs label suggests, and mention any upset to your pharmacist. |
For detail on medicines, see our guide to stinging nettle root and medicine interactions. For doses and forms, see dosage, timing and forms.
When to stop and get medical advice
The EMA advises seeing a doctor if complaints worsen or if fever, spasms, blood in the urine, painful urination or urinary retention occur during use ([1]). The NIDDK adds that some symptoms need urgent care: being unable to urinate at all, blood in the urine, painful, frequent and urgent urination with fever and chills, or great pain in the lower abdomen ([9]).
Stop and speak to a pharmacist or doctor if you notice itching, a rash or hives after taking nettle root, or if you have ongoing nausea, heartburn or diarrhoea. Seek urgent care for the symptoms listed above.
Long-term use, overdose and laboratory safety
Long-term use. The EMA monograph says long-term use is possible ([8]). The nettle-alone trials ran for 12 weeks to 12 months ([4], PMID 32981268; [3], PMID 15045190), the largest followed some men for up to 18 months ([1]), and the combination trial was followed for up to 96 weeks ([6], PMID 18038253).
Overdose. The EMA report states that no case of overdose has been reported ([1]). Follow the label of the product you use.
Laboratory safety. Some laboratory safety testing is still to be completed. The EMA report says adequate genotoxicity tests have not been performed and that no repeated-dose toxicity data are available ([1]). A review likewise notes that pre-clinical safety data remain to be completed ([2], PMID 17509841). On the basis of its traditional use, the EMA concluded that nettle root proved not to be harmful under the specified conditions of use ([1]).
Checking a product label
Because nettle root products differ in how they are made, a few checks help whichever product you choose:
- Plant part: make sure the label says root. Leaf is a different material, studied for different purposes.
- Extract ratio and serving size: a 10:1 extract uses about 10 parts of dried root for 1 part of extract, and the amount per capsule is the weight of the extract.
- Other ingredients: read the full ingredient list for fillers and anything you are sensitive to.
- Testing: look for a brand that can share independent test results for identity and contaminants.
- Directions: follow the serving on the label, or the advice of your healthcare provider.
Frequently asked questions
Is stinging nettle root safe?
In the clinical trials cited here, adverse events were few and not more frequent than with placebo, and, on the basis of its traditional use, the EMA concluded that nettle root proved not to be harmful under the specified conditions of use. Some groups should check with a doctor first: people allergic to nettle, people who are pregnant or breastfeeding, anyone under 18, and anyone with urinary symptoms that have not been checked.
What are the side effects of nettle root?
The EMA lists stomach and bowel complaints (nausea, heartburn, diarrhoea, constipation, fullness, gas) and allergic skin reactions (itching, rash, hives). Their frequency is listed as not known.
Can nettle root cause an allergic reaction?
Yes, it is possible. The EMA lists hypersensitivity as the contraindication and itching, rash and hives among the possible reactions. Stop taking it and speak to a pharmacist or doctor if you notice them.
Who should not take nettle root?
People who are allergic to nettle should not take it. It is also not recommended during pregnancy and breastfeeding, and it is not intended for people under 18. Anyone with unchecked urinary symptoms should see a doctor first.
Is nettle root safe during pregnancy or breastfeeding?
The EMA report says there is no information on reproductive and developmental toxicity, so use during pregnancy and breastfeeding is not recommended. Speak to your doctor if you are pregnant, planning a pregnancy or breastfeeding.
Is it safe to take nettle root every day for a long time?
The EMA says long-term use is possible. Nettle-alone trials ran for 12 weeks to 12 months, the largest followed some men for up to 18 months, and a combination trial was followed for up to 96 weeks. Review use with your doctor from time to time, and keep up regular prostate checks.
Does nettle root interact with medicines?
The EMA reports no interactions but says specific interaction data are not available, and the trials cited here did not test nettle root with other drugs. Ask your doctor or pharmacist first, especially if you take medicines for blood pressure, diabetes, blood thinning or BPH.
Can nettle root affect sexual function?
In a 48-week trial that compared a nettle root and saw palmetto combination with finasteride, fewer men on the combination reported reduced ejaculate volume, erectile dysfunction and headache. That trial tested the combination, not nettle root alone.
What happens if I take too much?
The EMA report states that no case of overdose has been reported. Follow the label, and contact a doctor or poison centre if you think you have taken too much or feel unwell.
Are the safety findings for nettle root the same as for nettle leaf?
Not necessarily. This guide covers the root. Nettle leaf is a different material studied for different purposes, so its findings should not be read across to the root.
The bottom line
Across the clinical trials and the EMA reports, nettle root has a favourable safety record: adverse events were few, and the reactions listed are mostly stomach and bowel complaints and allergic skin reactions. People who are allergic to nettle, pregnant or breastfeeding, under 18, taking regular medicines or living with unchecked urinary symptoms should speak to a doctor or pharmacist first, and anyone who notices worsening symptoms, blood in the urine, fever or painful urination should seek advice promptly.
Real Herbs Stinging Nettle Root Extract: 750 mg of 10:1 root extract per capsule (about 7,500 mg dried root equivalent), 100 vegetarian capsules. Backed by our 100-Day Money-Back Guarantee. Real Herbs sells this product. The trials and the EMA documents did not test this exact product.
Related reading
- Stinging nettle root for BPH: what the research shows
- Nettle root dosage, timing and forms
- Stinging nettle root and medicine interactions
References
- European Medicines Agency, Committee on Herbal Medicinal Products. Assessment report on Urtica dioica L.; Urtica urens L., radix. EMA/HMPC/322627/2023. Final, Revision 1, 22 January 2025. ema.europa.eu
- Chrubasik JE, Roufogalis BD, Wagner H, Chrubasik S. A comprehensive review on the stinging nettle effect and efficacy profiles. Part II: urticae radix. Phytomedicine. 2007;14(7-8):568-79. PMID 17509841 · DOI 10.1016/j.phymed.2007.03.014
- Schneider T, Rübben H. Stinging nettle root extract (Bazoton-uno) in long term treatment of benign prostatic syndrome (BPS). Results of a randomized, double-blind, placebo controlled multicenter study after 12 months (in German). Urologe A. 2004;43(3):302-6. PMID 15045190 · DOI 10.1007/s00120-004-0532-7
- Akbar Karami A, Sheikhsoleimani M, Reza Memarzadeh M, Haddadi E, Bakhshpour M, Mohammadi N, et al. Urtica Dioica Root Extract on Clinical and Biochemical Parameters in Patients with Benign Prostatic Hyperplasia, Randomized Controlled Trial. Pak J Biol Sci. 2020;23(10):1338-1344. PMID 32981268 · DOI 10.3923/pjbs.2020.1338.1344
- Lopatkin N, Sivkov A, Walther C, Schläfke S, Medvedev A, Avdeichuk J, et al. Long-term efficacy and safety of a combination of sabal and urtica extract for lower urinary tract symptoms--a placebo-controlled, double-blind, multicenter trial. World J Urol. 2005;23(2):139-46. PMID 15928959 · DOI 10.1007/s00345-005-0501-9
- Lopatkin N, Sivkov A, Schläfke S, Funk P, Medvedev A, Engelmann U. Efficacy and safety of a combination of Sabal and Urtica extract in lower urinary tract symptoms: long-term follow-up of a placebo-controlled, double-blind, multicenter trial. Int Urol Nephrol. 2007;39(4):1137-46. PMID 18038253 · DOI 10.1007/s11255-006-9173-7
- Sökeland J, Albrecht J. Combination of Sabal and Urtica extract vs. finasteride in benign prostatic hyperplasia (Aiken stages I to II). Comparison of therapeutic effectiveness in a one year double-blind study (in German). Urologe A. 1997;36(4):327-33. PMID 9340898 · DOI 10.1007/s001200050106
- European Medicines Agency, Committee on Herbal Medicinal Products. Community herbal monograph on Urtica dioica L., Urtica urens L., their hybrids or their mixtures, radix (nettle root). EMA/HMPC/461160/2008. Adopted 24 September 2012; marked superseded by the EMA. ema.europa.eu
- National Institute of Diabetes and Digestive and Kidney Diseases. Prostate enlargement (benign prostatic hyperplasia). Page reviewed June 2024. niddk.nih.gov
Disclaimer: This article is for educational purposes only and is not medical advice. Talk with a qualified healthcare professional before starting any supplement, especially if you have a medical condition or take medication. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
