Bearberry (Arctostaphylos uva)

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15. Safety and interactions

Warning signs. Fever, rigors, loin or back pain, vomiting or blood in the urine during a bladder infection can mean the infection has reached the kidney. That needs medical assessment the same day and usually an antibiotic, and bearberry is no treatment for it; REGATTA’s excess of kidney infections in the bearberry-first group is the reason this matters (section 13).

15.1 Adverse effects

• Gastrointestinal: nausea, vomiting and stomach-ache, frequency unknown [4]; attributed to tannin [5,6]; possible after as little as 15 g leaf in sensitive people (Frohne 2004) [5]. Bone and Mills add cramping and constipation at high doses [9]. Irritability, insomnia and a raised heart rate have also been reported in association with bearberry leaf extract (NTP 2006, as reported by the HMPC) [5].
• Urine discolouration: greenish-brown urine that darkens in air, from oxidised hydroquinone [4,6,8]. Harmless, but worth warning about.
• Trials and volunteer studies: ATAFUTI recorded two serious adverse events, both hospital admissions (an abdominal-wall abscess and right iliac fossa pain) judged unlikely to be or not related to treatment, and no upper-tract infection [25]. In 16 healthy volunteers given a single dose, blood count, clotting, electrolytes, liver and kidney tests and urinalysis showed no abnormality attributed to the extract (Schindler 2002, as reported by the HMPC) [5]. In REGATTA pyelonephritis or febrile UTI occurred in 9 of 207 women given bearberry first against 2 of 191 given fosfomycin [28]: an effect of withholding the antibiotic more than a toxic effect, but a real harm of the strategy.
• Eye: bilateral bull’s-eye maculopathy with paracentral scotomas and retinal thinning in a 56-year-old woman who drank bearberry tea for three years to prevent UTI, dose unknown (Wang and Del Priore 2004), attributed to inhibition of melanin synthesis [5,9]. One case report; causality is possible (long exposure, plausible mechanism, no dechallenge data in the sources read).
• Kidney: albuminuria, haematuria and casts have been linked to bearberry use in a secondary source (Adesunloye 2003, via the NTP) [5]; not assessable from what AIP has read.
• Liver: "chronic liver impairment" with prolonged use is stated in Barnes and Gruenwald [5,8] without a case report behind it in the sources read.
• Australian reports. In its 2019–2020 arbutin scheduling papers the TGA reported that the Database of Adverse Event Notifications held 38 cases between 01/01/1971 and 01/09/2019 in which Arctostaphylos uva-ursi was a listed active ingredient of a suspected medicine, 33 of them with a single suspected medicine, and none for products with arbutin itself as the active ingredient [40]. The reactions were not itemised. The live database sits behind a terms-of-use page and could not be queried by script in September 2026; the cases since 2019 and their reaction terms still need reading by a person.
• TGA safety alerts. A search of the TGA website in September 2026 for bearberry, uva ursi and arbutin found the scheduling papers and no safety alert, recall or product alert [39,40]; the TGA’s own site search and the recalls database did not answer an automated session, so this check is incomplete. Repeat web searches in October 2026 and October 2026 again found the scheduling papers and no safety alert or recall; on both dates the TGA site search returned a bot-challenge page and the Database of Adverse Event Notifications stopped at its terms-of-use page, so neither could be read by script.

15.2 Toxicology

• Hydroquinone is the constituent of toxicological interest. Oral LD50 320 mg/kg in rats, 400 mg/kg in mice, 550 mg/kg in guinea pigs, 200 mg/kg in dogs and 70 mg/kg in cats (Woodard 1949, as reported by the HMPC) [5]. In the NTP two-year gavage study (25 and 50 mg/kg, 5 days a week), male F344 rats developed renal tubule adenomas (4/55 and 8/55 against 0/55) against a background of worsened chronic progressive nephropathy, female rats mononuclear-cell leukaemia, and female mice liver adenomas [5,6]. Hydroquinone is genotoxic in several in vitro and intraperitoneal in vivo assays; oral results are mostly negative or weak [5].
• Arbutin: not mutagenic in V79 cells unless pre-incubated with β-glucosidase; no bone-marrow micronuclei in mice at 0.5–2 g/kg orally (Müller and Kasper 1996) [5,9]. Subcutaneous 400 mg/kg/day before mating and through pregnancy reduced fetal weight in rats; 100 mg/kg/day had no effect (Itabashi 1988) [5,6]; the HMPC judged the study of limited relevance to oral use because of the route and dose [5].
• Leaf and extract: an aqueous extract was negative in TA98 and TA100 (only 2 of the 5 recommended strains); a 70 % ethanol extract was negative in a micronucleus test not done to ICH standard; there are no repeat-dose, carcinogenicity or reproductive studies of the leaf [5]. The HMPC declined an EU "list entry" because genotoxicity data are inadequate [5]. That is why bearberry remains a traditional-use product in the EU with a one-week limit.
• Exposure. Free hydroquinone after a clinical dose is a fraction of a per cent of the arbutin dose [5]. A published risk assessment (Garcia de Arriba 2013) put the free hydroquinone from a recommended dose at about 11 per cent of the permitted daily exposure and concluded the margin is adequate for short-term use; it reaches this monograph through the HMPC, which accepted it [5].

15.3 Contraindications and cautions

15.4 Interactions

15.5 Overdose

No case of overdose has been reported [4]. Overdose is said to cause bladder and urinary-mucosa irritation, dysuria, haematuria and liver damage (Gruenwald; Hänsel) [5]; ten times the dose, tinnitus, breathlessness, convulsions, collapse, delirium and vomiting (NTP) [5]. Barnes quotes 1 g hydroquinone (6–20 g leaf) as causing such symptoms and 5 g as fatal [8]. None of these is supported by a case report in the sources read [5].

Referral. Anyone considering bearberry, and anyone with urinary symptoms that are recurrent, in pregnancy, in a man or in a child, should consult a degree-qualified herbalist with competencies and adequate training in pharmacognosy, who will also recognise when investigation and antibiotic treatment are needed.