Limited evidenceImmunity

Cistus Incanus

A polyphenol-rich Mediterranean rock rose with one placebo-controlled cold trial from 2009 that has never been replicated, plus cell-culture antiviral data that gets over-extrapolated into systemic immune claims.

What the science says

Upper respiratory tract infection symptoms Limited evidence
In a randomised, placebo-controlled trial of 160 patients with common cold, lozenges of the Cistus extract CYSTUS052 produced a significantly greater fall in subjective symptom score than placebo, and C-reactive protein dropped significantly in the treatment group. That is the entire clinical database: one manufacturer-linked trial, never independently replicated in the 15+ years since, with effect sizes not clearly quantified in the published abstract.
Antiviral activity is a surface effect, not a systemic one Limited evidence
The CYSTUS052 polyphenol extract blocked influenza virus in cell culture without cytotoxicity and without inducing viral resistance, apparently by binding viral surface proteins and physically preventing cell attachment. That mechanism fits a lozenge coating the throat — it is not a reason to expect systemic antiviral effects from swallowing tea, because polymeric polyphenols of this size are barely absorbed.
Lyme, biofilms and 'detox' claims Limited evidence
Cistus incanus appeared as one of seven active hits in a 2020 in-vitro screen against stationary-phase Borrelia burgdorferi at 1% extract concentration. There is no human trial in Lyme disease, and the popular claim that Cistus tea 'chelates heavy metals' or 'dissolves biofilms' in the body has no clinical support at all.

Dosage & safety

Studied doseThe URTI trial used CYSTUS052 lozenges dissolved slowly in the mouth several times daily over about a week. Commercial tea is brewed at 1-2 g of dried herb per cup, two to three cups daily; capsules are typically 400-500 mg. No dose-response work exists in humans.

SafetyGenerally well tolerated, with no significant safety signals in the one clinical trial. The high tannin content can cause nausea on an empty stomach and meaningfully impairs non-heme iron absorption — separate Cistus tea from iron supplements and iron-rich meals by at least two hours, which matters if you are anaemic or vegetarian. Cistus accumulates soil metals and some tea batches have shown elevated cadmium; buy tested product. No pregnancy or breastfeeding data. Not banned in sport.

Scientific references

Cistus incanus (CYSTUS052) for treating patients with infection of the upper respiratory tract. A prospective, randomised, placebo-controlled clinical study
Kalus U, Grigorov A, Kadecki O, et al. — Antiviral Res, 2009
A polyphenol rich plant extract, CYSTUS052, exerts anti influenza virus activity in cell culture without toxic side effects or the tendency to induce viral resistance
Ehrhardt C, Hrincius ER, Korte V, et al. — Antiviral Res, 2007

Where to buy

View on iHerb

Referral link — this site may earn a commission on purchases.

Related in Immunity

Vitamin C Limited evidence
Zinc Moderate evidence
Elderberry Limited evidence
L-Lysine Limited evidence
Echinacea Limited evidence
Andrographis Moderate evidence