The short answer
Aristolochic acid is a natural chemical in some plants used in herbal remedies. It causes urinary-tract cancers and kidney damage. Avoiding products that contain Aristolochia plants is the key step.
Aristolochic acid is classified as a known human carcinogen (IARC Group 1).
People are mainly exposed by taking herbal products that contain Aristolochia plants.
It is most strongly linked to cancers of the upper urinary tract.
A carcinogen classification describes hazard — whether something can cause cancer — not your personal risk at a given exposure.
Choose how you want to understand this
The full explanation.
The simple version
Aristolochic acid is a natural substance. It is found in a group of plants — Aristolochia and related species — used in some traditional herbal remedies. Taking products that contain it can damage the kidneys and cause cancers of the urinary tract.
What it is
Aristolochic acids occur naturally in birthwort and pipevine plants, and in some wild ginger plants. These grow worldwide. Herbal products made from them are sold for arthritis, gout, and inflammation. The FDA has not approved those products. They are often marketed as dietary supplements or traditional medicines.
How people are exposed
Common ways people come into contact with it:
- Taking herbal remedies or supplements that contain Aristolochia plants.
- Eating or drinking a herbal or food product that contains them without knowing it.
- Buying botanical products that are unregulated or mislabeled.
The cancer connection
Cancers of the upper urinary tract have been reported in people who took these products. The upper urinary tract means the renal pelvis and the ureters. Bladder cancer has been reported too. In these cases the herbal products had already caused kidney damage.
The International Agency for Research on Cancer (IARC) is the World Health Organization's cancer-research agency. It places aristolochic acid in Group 1, carcinogenic to humans. That is the strongest evidence category. It means there is enough evidence that the substance can cause cancer in people. The US National Toxicology Program agrees, listing aristolochic acid in its Report on Carcinogens as known to be a human carcinogen.
Hazard is not the same as risk
Two ideas are easy to mix up: hazard and risk. An agency that lists aristolochic acid as a carcinogen is talking about hazard. That means the substance can cause cancer under some conditions. It is not a statement about your own risk. Your risk depends on how much you are exposed to, for how long, and other factors. Two substances in the same group can carry very different real-world risks. The label answers "can it cause cancer?" It does not answer "how likely is it to cause cancer for me?"
How to lower your exposure
- Avoid herbal products that list Aristolochia, birthwort, or related plants.
- Buy supplements from trusted, regulated sources.
- Tell your doctor about every herbal product you take.
Are you looking at your overall cancer risk? Small, steady steps add up. To see where aristolochic acid sits among all the things that affect cancer risk, read our overview of cancer prevention and what raises cancer risk.
The bottom line
Aristolochic acid is a known human carcinogen (IARC Group 1). The most useful thing you can do is learn where exposure comes from. Then take reasonable steps to reduce it. Do not lose sleep over a single label. Put your energy into the biggest risks you can control in your own life.
Words to know
Tap any term to see what it means.
Common questions
Does aristolochic acid cause cancer?
Yes. Aristolochic acid is classified as a known human carcinogen, which means there is strong evidence it can cause cancer in people. How much any one person's risk rises depends on how much they are exposed to and for how long.
How are people exposed to aristolochic acid?
Most exposure happens by taking herbal products that contain Aristolochia plants.
Which cancers are linked to aristolochic acid?
It is most strongly linked to cancers of the upper urinary tract.
How can I reduce my exposure to aristolochic acid?
The main steps are avoiding herbal products that contain Aristolochia plants.
Does a carcinogen label mean I will get cancer?
No. A classification is about hazard — whether aristolochic acid can cause cancer under some conditions — not a prediction that any one exposed person will develop cancer. Your actual risk depends on the amount and length of exposure and other factors.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Speak With Trained Specialists & Human Navigators
Cancer Explained provides educational guidance, but does not replace trained specialists, social workers, or your medical team.
Talk to a trained cancer information specialist
Free, confidential assistance from NCI Cancer Information Service via phone, chat, or email.
Contact your oncology team
Locate after-hours contact numbers, portal messages, or urgent triage phone lines.
Find a patient navigator
Get one-on-one help with appointments, logistics, translation, and care coordination.
Find a genetic counselor
Discuss inherited mutation risk, family history, and genetic testing options.
Find an oncology social worker
Access emotional counseling, family support groups, and mental health resources.
Find a financial navigator
Locate copay assistance foundations, grant programs, and lodging/travel support.
Find a clinical-trial specialist
Search matching studies and speak with NCI trial information specialists.
Get urgent help
Immediate emergency guidance for fever (>100.4°F during chemo), severe pain, or shortness of breath.
Help Us Improve This Guide
Did this explanation answer your question and help you determine your next step?
Know someone who needs this?
Plenty of people are looking for something like this and do not know where to start. If this would help a friend or someone you love, send it on — we have written an opening line so you do not have to stare at an empty message. You can change every word of it.
Your message is written and sent in your own email or messaging app — we never see who you send it to, and nothing is added to any list.
Knowledge Check
0 of 2 answered
This self-assessment checks understanding of educational content only. It is not medical advice.
Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Last updated: 2026-08-11Next planned review: 2028-07-05
How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status — Source checked. This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
General education — varies by person. Answers genuinely differ between people. This page explains what commonly varies and points you to your care team for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
Read more about our editorial process, our use of AI, and our corrections policy.
Spotted a problem? Report an error — a factual mistake, broken or outdated source, confusing wording, or anything that seems unsafe. Please do not include names, medical record numbers, dates of birth, addresses, or other identifying medical information in your report.
After using this page, do you understand what to do next?
Anonymous — we only record the answer, never who gave it.
Related articles
Still have questions?
Educational answers, plain language
Free to print and share