Tos (general)

Andrographis is one of the most clinically studied herbs for upper respiratory tract infections (URTIs). Multiple RCTs and systematic reviews demonstrate significant reduction in URTI symptom severity and duration compared to placebo. The WHO formally lists prophylaxis and treatment of common cold, sinusitis, bronchitis, and pharyngotonsillitis among its documented clinical uses.

The pivotal 12-week RCT supporting arabinogalactan's respiratory benefits was specifically conducted during the cold season (2010/2011), making its findings directly applicable to seasonal respiratory health. LA significantly reduced cold episode incidence and the number of affected subjects during this high-risk period. The prebiotic-immune axis may confer broader seasonal immune resilience.

Astragalus membranaceus has been studied in a double-blind, placebo-controlled trial for seasonal allergic rhinitis with improved nasal symptoms. Its polysaccharides and astragalosides modulate immune function by correcting Th1/Th2 imbalance, reducing IgE, and suppressing pro-inflammatory cytokines. It is also a key immune-tonic herb in traditional Chinese medicine.

Bifidobacterium longum BB536 has been studied in randomized trials for seasonal allergic rhinitis, both as monotherapy and in combination probiotic mixtures. It was included in a combination trial in children with SAR and intermittent asthma showing symptomatic benefit, and is part of the 2016 meta-analysis evidence base of 22 RDBPCTs showing significant probiotic benefit for AR.

Bromelain, a proteolytic enzyme from pineapple stem, has anti-inflammatory and mucolytic properties relevant to seasonal respiratory health. Animal studies demonstrate reduced airway eosinophilic inflammation in asthma models. It is used clinically as an adjunct for nasal congestion and sinusitis and is frequently combined with quercetin in allergy protocols, also proposed to enhance quercetin bioavailability.

Butterbur (Petasites hybridus) leaf extract Ze 339 has been evaluated in multiple randomized controlled trials for seasonal allergic rhinitis. A landmark RCT in BMJ (2002) in 125 adults found butterbur as effective as cetirizine for symptom relief without sedation. A post-marketing surveillance study in 580 patients found 90% symptom improvement across rhinorrhea, sneezing, congestion, and eye itching.

Echinacea is one of the most extensively studied herbs for upper respiratory tract infections (URTIs). A 2019 systematic review and meta-analysis found a risk ratio of 0.78 (95% CI 0.68–0.88) for URTI prevention with Echinacea. The 2014 Cochrane review of 24 RCTs (4,631 participants) found mixed results for treatment of colds but acknowledged potential benefit from certain preparations. NCCIH and Cochrane both characterise the overall evidence as weak to modest.

E. purpurea has the most extensive clinical evidence base of all its applications in the prevention and treatment of seasonal upper respiratory tract infections. Multiple RCTs, a 2014 Cochrane review of 24 trials, and NCCIH/EMA recognition support this use, though results are heterogeneous across formulations.

Eucalyptus oil and its main constituent 1,8-cineole have been clinically studied across multiple respiratory conditions including the common cold, acute bronchitis, and sinusitis, with documented decongestant, mucolytic, bronchodilatory, and antimicrobial actions. Inhalation promotes airway clearance and reduces symptom burden. It is a widely used ingredient in inhalation therapies and chest rubs.

Elderberry has demonstrated benefit for acute viral respiratory illness through multiple RCTs and has traditional use for seasonal cold and flu prevention. The EMA and German Commission E recognize elderflower preparations for respiratory conditions. Its use as a seasonal preventive is supported by the Tiralongo 2016 travel trial.

Green chiretta has demonstrated preventive and symptom-reducing activity for seasonal respiratory illnesses. Pilot RCTs show that prophylactic use reduces the incidence of common colds during seasonal risk periods. Its immunomodulatory profile supports immune readiness during high-risk seasons.

Honey reduces cough frequency and severity in upper respiratory tract infections, which are the dominant seasonal respiratory ailment. A 2021 BMJ Evidence-Based Medicine systematic review and meta-analysis confirmed honey's effectiveness for symptomatic relief in URTIs. Its antibacterial and anti-inflammatory properties may also reduce secondary bacterial superinfection during seasonal illness.

Honeysuckle is one of the most extensively used TCM herbs for upper respiratory tract infections, with antiviral activity against influenza A, RSV, and other respiratory viruses documented in published pharmacological studies. It is a core ingredient in Yin Qiao San, a widely studied formula for wind-heat colds.

Lactobacillus acidophilus is frequently included in probiotic clinical trials for allergic rhinitis. It appears in the 2016 meta-analysis of 22 RDBPCTs for AR and was specifically included in a 2024 multi-strain probiotic RCT for seasonal AR that significantly reduced rhinoconjunctivitis symptom scores during pollen season.

Lactobacillus casei Shirota was assessed in a 16-week RDBPCT of 60 SAR adults, showing favorable immunological changes at the nasal mucosa following allergen challenge. It is one of the probiotic strains within the dataset of the 2016 meta-analysis of 22 RDBPCTs demonstrating significant AR symptom benefit for probiotics.

Lactobacillus paracasei strains are among the most consistently studied probiotics for seasonal allergic rhinitis. A 2016 meta-analysis of 22 RDBPCTs found all five L. paracasei studies demonstrated clinically significant symptom improvements vs. placebo, with significant reductions in nasal (SMD -1.23, p<0.001) and ocular (SMD -1.84, p<0.001) symptom scores.

Lactobacillus rhamnosus strains have been studied in RCTs for seasonal allergic rhinitis. A 2016 meta-analysis of 22 RDBPCTs found probiotics including Lactobacillus strains produced significant reductions in nasal and ocular symptom scores (SMD -1.23, p<0.001 and SMD -1.84, p<0.001) and quality-of-life measures vs. placebo in allergic rhinitis.

Luteolin is a flavone identified as the active anti-allergic component of Perilla frutescens and found in many edible plants. In allergic rhinitis mouse models, it significantly reduced allergic symptoms, IgE, eosinophil infiltration, and IL-4-secreting T cells, and reduced CD4+IL-4-secreting cells in human AR patient PBMCs in vitro. Evidence is primarily preclinical with mechanistic support.

Malabar nut's expectorant, bronchodilatory, antitussive, and anti-inflammatory properties make it a documented seasonal respiratory remedy in Ayurveda and Unani, with supporting evidence from clinical trials of combination products for acute upper respiratory infections.

Marshmallow root has clinical and regulatory support for soothing irritated upper respiratory mucosa and relieving dry cough. The German Commission E approved it in 1989 for oral/pharyngeal mucosa irritation and dry cough. A 2018 prospective observational study (n=822) confirmed symptomatic benefit in dry cough users. Animal and human data confirm antitussive polysaccharide activity.

Menthol inhalation significantly improves subjective nasal airflow sensation in subjects with nasal congestion from common cold, though objective nasal resistance does not decrease. It also reduces respiratory discomfort and modulates respiratory reflexes via TRPM8 activation.

Stinging nettle (Urtica dioica) has preliminary evidence for seasonal allergic rhinitis. A randomized, double-blind, placebo-controlled trial showed significant improvement in SNOT-22 symptom severity and reduction in nasal eosinophil counts. In vitro studies confirm inhibition of mast cell degranulation, histamine activity, and prostaglandin formation, though NCCIH rates evidence as inconsistent and limited.

Menthol, peppermint's principal active component, is well-established as a nasal decongestant and is widely used in over-the-counter respiratory products for colds, sinusitis, and upper respiratory tract infections. Menthol acts on TRPM8 cold receptors in the nasal mucosa, creating the sensation of improved airflow. Human studies on respiratory tract effects of peppermint are documented in the peer-reviewed literature.

Perilla frutescens leaf extract, rich in rosmarinic acid and luteolin, was tested in a randomized, double-blind, placebo-controlled trial for seasonal allergic rhinoconjunctivitis showing significant symptom improvements and reduced inflammatory cell infiltration. It inhibits mast cell degranulation and leukotriene/prostaglandin synthesis, and is used traditionally in East Asian medicine for respiratory allergies.

Quercetin is a flavonoid that stabilizes mast cells and inhibits histamine release, with preclinical and early clinical evidence for seasonal allergic rhinitis. A 2022 randomized, double-blind trial found significant symptom reduction, and a 2025 PRISMA-compliant systematic review of 18 studies confirmed consistent anti-allergic effects. Human studies show superior symptom improvement when added to standard therapy.

Rosmarinic acid, concentrated in Perilla frutescens and also found in rosemary and other herbs, was tested in a 21-day randomized, double-blind, placebo-controlled trial in seasonal allergic rhinoconjunctivitis patients. Active treatment significantly increased responder rates for itchy nose, watery eyes, itchy eyes, and total symptoms, and significantly reduced neutrophils and eosinophils in nasal lavage fluid.

Serratiopeptidase's mucolytic and anti-inflammatory actions are relevant to seasonal respiratory conditions involving mucus hypersecretion and mucosal inflammation. Clinical trials in ENT disorders and chronic sinusitis support benefit for rhinitis-type symptoms including nasal obstruction and excessive secretions. No specific seasonal allergy RCTs exist; extrapolation is from sinusitis and ENT trial data.

Spirulina, a blue-green alga, was studied in a double-blind, placebo-controlled clinical trial (Eur Arch Oto-Rhino-Laryngol, 2008) for allergic rhinitis, showing significant improvements in nasal discharge, sneezing, congestion, and itching. Its active pigment C-phycocyanin inhibits histamine release from mast cells and selectively inhibits COX-2. A comparative trial also found it comparable to cetirizine.

Thyme has the strongest clinical evidence base of any of its applications. Multiple randomized, double-blind, placebo-controlled trials support thyme-based herbal medicinal products (thyme/ivy and thyme/primula combinations) for reducing cough frequency, bronchitis severity, and symptom duration in acute upper respiratory tract infections. The German S3 guideline on cough and the WHO both recognize its use.

Thymus vulgaris preparations are EMA-recognised for productive coughs associated with cold season and upper respiratory infections, with clinical trial evidence for cough reduction. Thyme's combined antimicrobial, spasmolytic, and expectorant actions make it relevant to seasonal respiratory challenges. Traditional and clinical use is well-documented in European phytotherapy.

Tinospora cordifolia was evaluated in a randomized, double-blind, placebo-controlled trial in 75 allergic rhinitis patients over 8 weeks. Treatment produced significant reductions in sneezing (83%), nasal discharge (69%), nasal obstruction (61%), and nasal pruritus (71%) compared to placebo. It is also referenced in integrative medicine reviews as an evidence-based herbal option for allergic rhinitis.

Vitamin C has antioxidant and antihistamine properties with evidence for reducing histamine levels and supporting immune function in allergic rhinitis. It has been included in at least one RDBPCT-tested multicomponent supplement for seasonal AR in children with favorable results. It is referenced by NIH ODS as supporting immune function relevant to seasonal respiratory health.

Vitamin D3 plays an immunomodulatory role in respiratory allergy, with epidemiological evidence linking deficiency to increased allergic rhinitis severity and a dedicated clinical trial (Bakhshaee et al., Eur Arch Oto-Rhino-Laryngol, 2019) showing supplementation improved AR symptoms. It promotes Treg development, suppresses Th2 polarization, and reduces IgE production.

Zinc has immunomodulatory properties with evidence for reducing allergic responses in an allergic rhinitis mouse model through p38 MAPK pathway modulation (J Trace Elements Med Biol, 2023). It was also included in an RDBPCT-tested multicomponent supplement (quercetin phytosome + zinc + vitamin C) for seasonal AR in children with favorable results.

A. spectabilis is broadly used in Himalayan traditional medicine for seasonal respiratory conditions including coughs, colds, bronchitis, and asthma. Multiple ethnobotanical surveys from Nepal and India document this seasonal respiratory use.

Bayberry was traditionally used in composition powder and herbal formulas specifically for seasonal respiratory ailments including winter colds, chills, and associated sinusitis. The herb is documented in multiple herbal systems for these seasonal conditions. No clinical evidence supports this use.

Black spruce is used in traditional aromatherapy for seasonal respiratory support including seasonal allergies, catarrh, and congestion. Aromatic phytoncides from conifers including spruce have documented effects on stress and immune markers relevant to seasonal health management.

Coltsfoot has extensive traditional use across Europe and Asia for seasonal respiratory complaints including coughs, congestion, and irritated airways. Its expectorant, demulcent, and antispasmodic actions are well-described in herbal traditions. No controlled human trials exist.

Elecampane has been used across multiple traditional systems as a respiratory tonic for coughs and mucus-related complaints, aligning with seasonal respiratory challenges. Its expectorant and antibacterial properties underpin this traditional role. No clinical trials have assessed seasonal respiratory use specifically.

Eyebright (Euphrasia officinalis) has been used in traditional European herbal medicine since the Middle Ages for eye and upper respiratory conditions associated with seasonal allergies, including hay fever, itchy watery eyes, and rhinitis. Its flavonoids (luteolin, quercetin) have in vitro antihistamine and mast cell-stabilizing properties. Direct human RCT evidence for oral use in seasonal AR is lacking.

Fritillary is extensively used in TCM formulas for seasonal respiratory complaints including wind-heat and wind-cold patterns. TCM texts and the Chinese Pharmacopoeia reference its use for cough and phlegm arising in seasonal respiratory infections. No controlled seasonal or allergy-specific human trials exist.

Garlic has been used across multiple traditional medical systems (Chinese, Japanese, Ayurvedic, indigenous North American) as a seasonal preventative for respiratory ailments during cold and flu season. Its antimicrobial, immunomodulatory, and anti-inflammatory properties provide biological plausibility. Clinical RCT evidence specific to seasonal respiratory defense is limited to the single Cochrane-reviewed cold prevention trial.

Goldenrod has a documented traditional role for seasonal upper respiratory conditions including colds, flu, and seasonal catarrh. It has been used as a hot infusion diaphoretic for influenza and as a gargle for laryngitis in the European herbal tradition. Its anticatarrhal, anti-inflammatory, and mild antimicrobial properties support this use.

GMT's EU herbal monograph (EMA/HMPC) formally recognizes traditional use for relief of cough associated with cold, placing it firmly in the seasonal respiratory health category. GMT has been used across the Balkan region for centuries as a seasonal tea during cold and flu season, valued for its expectorant, antimicrobial, and immune-supportive properties.

Horehound is one of the oldest documented respiratory remedies, used across European, Egyptian, and Ayurvedic traditions for catarrh, cough, and bronchial congestion associated with seasonal respiratory episodes. The EMA HMPC recognises its traditional use for cough related to upper respiratory tract symptoms. Its inclusion in commercial formulations such as Ricola lozenges reflects ongoing practical use.

Horseradish has a long herbal tradition for seasonal respiratory complaints, including hay fever and sinus congestion. A sandwich of freshly grated root is a recorded traditional remedy for hay fever. The pungent volatile isothiocyanates are believed to clear nasal passages and stimulate mucosal secretion. No clinical trials address seasonal allergic rhinitis specifically.

Hyssop has a long history of use for seasonal respiratory ailments, including colds, influenza, and mucous congestion. Traditional herbalism recommends it as an expectorant and diaphoretic herb that supports the body during febrile respiratory illness. Its volatile oils are considered to provide relief for mild upper respiratory irritations.

Documented traditional use in Mediterranean Europe for seasonal respiratory conditions including allergies, colds, and cough; provides a consistent pattern of folk use for supporting respiratory function seasonally. Scientific evidence is confined to in vitro antimicrobial and anti-inflammatory mechanisms.

I. racemosa is traditionally used in Ayurveda and Himalayan ethnomedicine for seasonal respiratory conditions including cough, congestion, and breathlessness that worsen with seasonal changes. It is classified as kapha-reducing, with expectorant, bronchodilator, and antihistamine properties relevant to seasonal respiratory variation.

Lobelia has longstanding traditional use for seasonal respiratory conditions including bronchitis, coughs, and bronchial congestion associated with seasonal respiratory illness. It acts as an expectorant and bronchodilator. Native Americans smoked it for respiratory complaints; Eclectic physicians prescribed it for bronchopulmonary affections. No human clinical trials exist.

Mullein is one of the most historically established herbal remedies for seasonal respiratory complaints including winter coughs, bronchial congestion, and cold-season airway irritation. Its expectorant saponins and demulcent mucilage provide the mechanistic basis. Evidence is traditional and pre-clinical, with no dedicated seasonal respiratory RCTs.

P. orientalis is traditionally used for respiratory ailments associated with seasonal changes, including coughs, bronchitis, and cold-related conditions. Multiple ethnopharmacological records and systematic reviews document this broad respiratory support role.

Pine has been used across Native American and traditional aromatic medicine for seasonal respiratory health, particularly for colds, flu, and seasonal respiratory infections. Pine needle tea rich in vitamin C has been used for immune support. Traditional steam inhalation with pine is used to support respiratory tract health during cold and flu season.

Plantago lanceolata is used traditionally across Europe for seasonal respiratory symptoms including catarrh, coughs, and mild inflammation associated with seasonal changes. Its endorsement by the Commission E and ESCOP for catarrh of the airways extends to seasonal presentations. Traditional use in herbal teas and syrups for seasonal colds is well-documented.

Plantain has a long tradition of use in European and Asian herbal medicine for seasonal respiratory complaints including catarrh, excess mucus, and cold-related cough. Its documented demulcent, expectorant, and mild antimicrobial properties support this use. No dedicated RCTs exist specifically for seasonal respiratory health as a distinct indication.

Platycodon root is widely employed in TCM, Kampo, and Korean traditional medicine seasonal formulas for upper respiratory tract support during autumn and winter, addressing cough, phlegm, and throat irritation. This use is documented in pharmacopoeias across Northeast Asia, though no seasonal-specific clinical trials exist.

Across Chinese, Korean, and Japanese traditional medicine systems, platycodon root is a canonical remedy for seasonal respiratory ailments including coughs, congestion, and throat irritation associated with seasonal changes. The Chinese Pharmacopoeia lists these as official indications. Preclinical evidence supports expectorant, anti-inflammatory, and antiviral mechanisms relevant to seasonal respiratory conditions.

Traditional use of Quillaja bark in South American ethnomedicine for cough, chest congestion, and respiratory complaints provides an indirect basis for its association with seasonal respiratory support. No specific clinical data address seasonal conditions.

In TCM, siler root is a primary herb for wind-cold seasonal respiratory illness—colds, chills, nasal congestion, and early-stage flu—especially during seasonal transitions. It appears in approximately 8% of Chinese Pharmacopoeia prescriptions. Preclinical evidence supports antipyretic and anti-inflammatory activity, but no human clinical trials have established efficacy for seasonal respiratory health specifically.

Spruce needle oil and shoot preparations are traditionally used during cold and flu season to support respiratory health through expectorant, antiseptic, and mucolytic actions. Registered European herbal preparations containing Norway spruce are marketed for seasonal respiratory complaints. Spruce vitamin C content in needles was historically important for winter health.