Adulteration and Substitution in Chinese Herbal Products
What adulteration and substitution mean in Chinese herbal products, with dated regulator warnings, documented examples, and what research can and cannot say about how common they are.
Content last updated . This page has not been medically reviewed.
Three different problems
People often use "contaminated" and "fake" loosely. They are different problems with different causes:- Adulteration with drugs. A pharmaceutical is added, on purpose, without being listed. This is fraud.
- Substitution. One plant is swapped for another, by mistake or to save money, often because the names or appearance are similar.
- Contamination. Heavy metals, pesticides, mould toxins or other plant material get in during growing, drying, storing or making.
Quality control problems also include wrong processing (some herbs are traditionally processed to reduce toxicity). This page is information only. For heavy metals see heavy metals in Chinese medicines; for the drug cases see undeclared drugs in Chinese patent medicines.
How common is it? Honest answer: unclear
Evidence is real but patchy. A 2002 review concluded that evidence of toxic heavy metals and undeclared drugs in Asian herbal medicines might constitute a serious health problem, but that most of the data was anecdotal and insufficient to define how common it is. [1] A later overview of 26 systematic reviews reported adulteration or contamination with pesticides, heavy metals and prescription drugs, and said contamination was most often reported for Chinese remedies. [2] A 2025 meta-analysis of 22 studies on weight-loss "natural" products (not only Chinese) found a median of 37.5% with synthetic adulteration, ranging from 0% to 100%. [3]These numbers come from tested samples picked for study, often products already suspected. They do not tell you the chance that a given product on your shelf is affected. In a Harvard study of 334 raw Chinese herb samples from China, every sample had at least one metal detectable; the authors judged that most would be of negligible concern at likely consumption, but not under the most conservative scenario, and advised more monitoring. [4]
Documented examples
| What | What the source says | Where |
|---|---|---|
| Aristolochic acid | FDA says several outbreaks of renal failure were tied to Chinese herbal medicines later shown to contain aristolochic acid, because the plant on the label was misidentified or was confused with an aristolochia-containing ingredient since "traditional Chinese names were misinterpreted or similar". [5] | US (FDA import alert) |
| Ephedra | FDA recalled a Chinese patent medicine because it contained undeclared Ephedra herba (ma huang), a banned item. [6] | US recall, 2017 announcement |
| Herbal tea with drugs | Hong Kong's Department of Health found herbal tea from three shops containing paracetamol, or paracetamol and chlorpheniramine, and told shops to stop selling it. [7] | Hong Kong, 2009 |
| Herb mix-up | In Hong Kong, a toxic flower (Flos Daturae Metelis) substituted for a non-toxic one (Flos Campsis) was a main cause of anticholinergic poisoning. [8] | Hong Kong, 1989 to 2012 |
| Look-alike plant | Hong Kong health officials said a non-toxic plant resembles toxic ones and "can be mixed up with these substances". [9] | Hong Kong, 2015 |
| Five Flowers Tea | Of 33 market samples, DNA tests confirmed ten adulterants and an insect in some. [10] | Hong Kong market study |
The Hong Kong poisoning review gave overall incidence of herbal-medicine anticholinergic poisoning as 0.06 per 100,000 population in 2008 to 2012 (0.03 in 2000 to mid-2005), so serious cases are uncommon but not zero. [8]
What FDA says about hidden ingredients
FDA says hidden ingredients are often prescription drug ingredients, banned substances or harmful chemicals; the contaminated products it identifies are only a small fraction of what is on the market, and a product missing from its list is not shown to be safe. [11] FDA's import alert for aristolochic acid says a product with a small amount "could be used for years with no apparent adverse effects until serious, irreversible effects, such as renal damage, has occurred". [5] That is why "I have used it for years" is not proof of safety.What reviewers recommend
The Hong Kong poisoning review called for studies along the supply chain to find likely sources of contamination, regular inspection of retailers, and continuing education for staff in the herbal trade. [8] The overview of 26 systematic reviews concluded that more stringent quality control and enforcement seem necessary. [2] Laboratory tools such as DNA barcoding and chemical fingerprinting are the main research areas for detecting adulteration of Chinese herbs. [12]What you can do
- Use products from sellers who can name the exact species, part used and batch. See buying Chinese herbs safely and reading a Chinese patent medicine label.
- Tell your doctor and pharmacist what you take, including tea and soup herbs. NCCIH notes that contaminants found in some products include drugs such as warfarin and diclofenac. [13]
- Stop and seek care if you feel unwell. Report problems: reporting problems with Chinese herbs.
- In the US, Poison Help is 1-800-222-1222 and the emergency number is 911. See Poison Help by country.
What this does not mean
It does not mean all Chinese herbal products are unsafe, and it does not mean regulated Western supplements are always clean. The problem is quality control, and it exists in many herbal products. See natural and traditional do not mean safe.Frequently asked questions
What is the difference between adulteration and substitution?
Adulteration usually means something extra was added, such as an undeclared drug. Substitution means a different plant was used in place of the named one, often by mistake because the plants look or sound alike. [8][5]
Are Chinese herbs more often adulterated than other herbal products?
Reviews report problems across Asian and other herbal products. One overview said contamination was most often noted for Chinese remedies and adulteration for Indian ones, but the underlying data are uneven. [2]
Which drugs have been found in Chinese herbal products?
NCCIH names warfarin and diclofenac as examples. Hong Kong found paracetamol and chlorpheniramine in herbal tea. A meta-analysis of weight-loss natural products found sibutramine the most common adulterant. [13][7][3]
Can testing at home tell me?
Not in a reliable way that we found. The studies that detect adulterants use laboratory methods such as DNA sequencing. [14]
What should I do if I think a product made me ill?
Stop it, keep the package, seek medical care, and tell the clinician what you took. In the US, you can call Poison Help at 1-800-222-1222.
References
- Ernst E. Toxic heavy metals and undeclared drugs in Asian herbal medicines. Trends Pharmacol Sci 2002. Read 2026-10-22.
- Posadzki P, Watson L, Ernst E. Contamination and adulteration of herbal medicinal products: an overview of systematic reviews. Eur J Clin Pharmacol 2013. Read 2026-10-22.
- Phan DTA et al. Pharmaceutical adulteration in weight-loss natural products: systematic review and meta-analysis. Front Pharmacol 2025. Read 2026-10-22.
- Harris ES et al. Heavy metal and pesticide content in commonly prescribed individual raw Chinese Herbal Medicines. Sci Total Environ 2011. Read 2026-10-22.
- Import Alert 54-10, Aristolochic Acid, US FDA. Read 2026-10-22.
- Kingsway Trading Inc. recall of Xanthium & Siler Combo (Bi Yan Pian), US FDA. Read 2026-10-22.
- Chinese herbal tea found adulterated with western drug ingredients, Hong Kong Government news, 16 June 2009. Read 2026-10-22.
- Chan TYK. Herbal Medicines Induced Anticholinergic Poisoning in Hong Kong. Medicines 2016. Read 2026-10-22.
- CHP investigates suspected poisoning case after consumption of medicinal plants, Hong Kong Government news, 16 July 2015. Read 2026-10-22.
- Ethnopharmacology of five flowers herbal tea, a popular traditional beverage in Hong Kong and South China, J Ethnobiol Ethnomed 2024. Read 2026-10-22.
- Avoiding Products Contaminated with Hidden Ingredients, US FDA. Read 2026-10-22.
- Luo Y et al. Systematic review on fingerprinting development to determine adulteration of Chinese herbal medicines. Phytomedicine 2024. Read 2026-10-22.
- Traditional Chinese Medicine: What You Need To Know, NCCIH. Read 2026-10-22.
- Coghlan ML et al. Deep sequencing of plant and animal DNA contained within traditional Chinese medicines. PLoS Genet 2012. Read 2026-10-22.