Licorice Root for Allergies? What the Research Says

Key Findings

This systematic review analyzed multiple Traditional Chinese Medicine (TCM) formulations for allergic rhinitis (AR), identifying licorice root (Glycyrrhiza glabra) as a key component in several effective multi-herb formulas. The review concluded that licorice root contributes to AR symptom relief primarily through anti-inflammatory and immunomodulatory mechanisms, including inhibition of histamine release, suppression of Th2 cytokines (e.g., IL-4, IL-5, IL-13), and reduction of IgE levels. It emphasized that licorice is rarely used alone in TCM for AR but enhances efficacy in synergistic combinations like Xin-Yi San or Bi Min Gan granules. No isolated licorice root clinical trial data were presented, as the review focused on multi-herb formulations.

Study Design

This was a systematic literature review (not a primary clinical trial) published in January 2022. The methodology involved searching PubMed, Web of Science, and CNKI databases for English and Chinese studies on TCM mechanisms in AR treatment up to 2021. It synthesized findings from 127 eligible studies (including in vitro, animal, and human trials), but no specific sample size, demographics, or trial duration were provided for licorice root itself, as it was evaluated only within multi-herb contexts. The review assessed mechanistic pathways and clinical outcomes across heterogeneous TCM formulas.

Dosage & Administration

The review reported that licorice root in TCM formulas for AR is typically administered as part of a decoction or granule. Standard TCM dosing ranges of 3–9 grams per day of dried licorice root were noted, but exact doses varied across the cited studies depending on the specific formula (e.g., Xin-Yi San contains 6g licorice per daily dose). Administration was oral, usually as a tea or dissolved granules, for periods ranging from 2 weeks to 3 months in the included clinical trials.

Results & Efficacy

The review highlighted that licorice-containing formulas significantly reduced AR symptoms (sneezing, rhinorrhea, nasal itching) compared to placebo or antihistamines in multiple cited studies. For example, one referenced trial noted a 68.5% total effective rate for Bi Min Gan granules (containing licorice) versus 45.7% for loratadine (p < 0.05). Mechanistic data showed licorice compounds (glycyrrhizin, liquiritin) reduced serum IgE by 25–40% and nasal eosinophils by 30–50% in animal models. However, no isolated licorice root efficacy data, effect sizes, or confidence intervals were quantified, as results were aggregated across multi-herb interventions.

Limitations

Key limitations include: (1) No primary data—findings are derived from heterogeneous studies with varying designs, making direct attribution to licorice root impossible; (2) Lack of standardized dosing for licorice across formulas; (3) Potential publication bias toward positive TCM outcomes in included studies; (4) Inadequate safety reporting for licorice-specific risks (e.g., hypertension from glycyrrhizin); (5) Most human trials had small samples (<100 participants) and short durations. Future research should isolate licorice’s effects and establish dose-response relationships.

Clinical Relevance

For supplement users, this review suggests licorice root may support AR management only as part of professionally formulated TCM combinations, not as a standalone supplement. Self-administering isolated licorice root risks adverse effects (e.g., hypokalemia, hypertension) due to glycyrrhizin. Users should consult a TCM practitioner for personalized formulas and avoid long-term/high-dose use (>100 mg glycyrrhizin/day). The evidence does not support over-the-counter licorice supplements for AR without clinical supervision, given the lack of isolated efficacy data and safety monitoring in the reviewed studies.