Last updated: November 30, 2020
Now more than ever, practitioners and patients are focusing on natural supplements for immune system support to counteract pathogens that cause respiratory tract infections, and modulate the immune and anti-inflammatory responses to these pathogens.
Unfortunately, some of the best supplements for immune system support, such as echinacea, vitamin C, zinc, elderberry, probiotics, and vitamin D, are in high demand, and at times, even difficult to find. However, there are many alternative natural ingredients that can be effectively used to fight off pathogens, support immunity, and treat symptoms of respiratory tract infections.
This article provides a high-level overview of respiratory tract infections, and several alternative natural supplements for immune system support that can be used to combat respiratory tract infections. These ingredients can support various pathological mechanisms that either combat pathological infection, or reduce the host’s physiological response to infection to ultimately reduce the severity of respiratory tract symptoms.
Please note that there are many more ingredients that can be used for immune and respiratory support that are not currently included in this article. Future editions will provide additional information on ingredients not currently covered in this version.
Pathogenesis and pathophysiology of respiratory tract infections
There are several origins (pathogenesis) and physiological outcomes (pathophysiology) related to respiratory tract infections. Viruses are one of the most common causes of respiratory tract infections. The human rhinovirus, respiratory syncytial virus, influenza virus, parainfluenza virus and other viruses can result in respiratory infection in infect individuals of all health and age statuses. They may lead to a variety of acute airway conditions, or other disorders such as asthma, bronchitis, chronic obstructive pulmonary disease (COPD), the common cold, the flu, or pneumonia to name a few. (72)
Respiratory tract infections are not only caused by viruses, however. Bacterial colonization is another means by which both upper respiratory infection and lower respiratory infection may occur. (91) Most commonly, Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis are the bacteria involved in respiratory tract infections. (6)
The body’s response to the presence of pathogens like viruses or bacteria can lead to an overstimulation of the inflammatory response and immune system. The host’s immune and inflammatory hyper-response can cause a prolonged or more severe reaction to infection, leading to increased prevalence of symptoms associated with infection such as chills, coryza, cough, fever, headaches, myalgia, rhinorrhea, shortness of breath, sneezing, sore throat, sputum production, wheezing, and occasional gastrointestinal complications such as nausea or vomiting. These symptoms typically depend on the specific pathogen and can ultimately lead to the damaging of respiratory tract damage. (66)
Two of the most well known causes of respiratory tract infections involve viruses that cause the common cold and influenza. Several symptoms of cold and flu respiratory system infections are shown below.
Alternative ingredients for immune system and respiratory system support
Numerous ingredients provide a variety of pharmacological actions that may physiologically increase the body’s ability to fight off pathogens that cause symptoms of the respiratory tract, or the development of more severe respiratory conditions.
These ingredients can also provide relief from the symptoms associated with infections of the respiratory tract. For reference, the American Botanical Council (ABC), one of the leading sources for information on botanical and alternative medicine, has amassed terminology related to natural ingredient actions and their properties.
The terms that apply to the mechanistic uses of natural ingredients relating to the counteraction of respiratory pathogens and the reduction of symptoms caused by respiratory tract infections are summarized here:
- Anti-catarrhal: reduces head and throat mucosal inflammation
- Anti-inflammatory: reduces inflammation in response to infection
- Anti-microbial: opposes microbes (eg. bacteria, viruses)
- Anti-spasmodic: reduces bronchi/upper lung spasms or constriction to improve breathing
- Anti-tussive: stops or reduces cough
- Demulcent: polysaccharide-rich ingredients to cover and alleviate inflamed mucous membranes
- Diaphoretic: induces sweating
- Expectorant: helps to remove secretions
- Febrifuge: reduces fever (3)
The following figure summarizes some of the main uses of several natural ingredients and their main mechanistic applications in immunity and respiratory support.
The main uses were selected based on a mix of available human, in vivo and in vitro evidence, and/or a history of reported traditional use in respiratory conditions. The table at the end of this article presents more detail on the evidence supporting the main uses of these ingredients.
Disclaimer: The ingredients listed below and in the diagram are categorized based on a main mechanism of action within the respiratory system. However, they may have more than one application within and outside of the respiratory system. The main actions were selected based on a combination of available evidence and based on knowledge obtained from the ingredient’s traditional history of medicinal use as reviewed by Fullscript’s Integrative Medical Advisory Team.
For an explanation of the classes of evidence as shown below (A, B, C, D, E, and F), please see the Rating Scales for Evidence-Based Decision Support.
The following ingredients may be used in applications related to mucosal inflammation in the head and neck.
Andrographis (Andrographis paniculata)
- Reduces the overall symptoms of upper respiratory tract infections, particularly for cough and sore throats – A (10)(40)(50)(73)
- Reduces severity and duration of other symptoms of the common cold, such as chills, earaches, fatigue, headaches, muscle soreness, and rhinitis – B (8)(28)(36)(63)(64)(79)(94)(103)
- Traditionally used to treat infectious diseases, which may translate to the reduction of catarrh – F (10)(40)(50)
- Nasal drops or inhaled: reduce rhinitis symptoms including congestion, runny nose, sneezing, mucosal edema, pallor, and peripheral eosinophil counts – C/D (47)(114)
- Traditionally used for their healing properties, with many applications in catarrhal diseases – F (22)
Propolis (Apis mellifera)
- Reduces rhinitis symptoms within ~4 days and resolution of infectious rhinovirus symptoms by ~4-5th day – D (61)(100)
- Reduces incidence of acute/chronic symptoms of rhinopharyngitis, and presence of viral microflora in upper airways – D (11)
- Traditionally used primarily for its anti-microbial and anti-inflammatory properties, (7) which may translate into its use in infections of the upper respiratory tract – F (123)
Sage (Salvia officinalis)
- Reduces sore throat symptoms with similar efficacy to chlorhexidine/lidocaine sprays – B (42)(81)
- Traditionally used to relieve oral and throat inflammation – F (107)
The following ingredients may be used to reduce inflammation in response to pathogenic infection.
Feverfew (Tanacetum parthenium)
- Reduces epithelial, basal membrane, & subepithelial smooth muscle thickness (histologic parameters in asthmatic lung), and IL-4 inflammatory marker in vivo – D (5)
- Reduces inflammatory cell infiltration, airway permeability, production of inflammatory cytokines, and stimulation of NF-κB phosphorylation that leads to acute lung injury in vivo & in vitro – D/E (43)
- Reduces 5-LOX, PDE3 & PDE4 inflammatory enzymes activities, release of macrophage NO, PGE(2), & TNF-ɑ, and human PBMC TNF-ɑ, IL-2, IL-4, & IFN-γ in vitro – E (96)
- Traditionally used in inflammatory conditions – F (69)
Honeysuckle (Lonicera japonica)
- Increases IL-10 anti-inflammatory cytokine in vivo – D (46)
- Reduces NF-κB phosphorylation to prevent lung expression of PGE2, TNF-α, IL-1β and IL-6 in response to inflammatory stimuli in vivo – D (46)(70)(102)
- Traditionally used to treat conditions related to inflammation and infection – F (54)
Licorice (Glycyrrhiza glabra, Glycyrrhiza uralensis)
- Reduces neutrophil infiltration causing reduced TNF-α, & IL-1β release, and consequential neutrophil recruitment to provide antioxidative activity in the lung in vivo – D (116)
- Reduces COX-2, NO, TNF-α, ICAM-1 in vivo – D (121)
- Traditionally used in the treatment of inflammatory conditions including those of the respiratory tract like sore throats, cough, or asthma – F (21)
The following ingredients may be used in applications related to the opposition of microbes such as bacteria or viruses that cause respiratory distress.
Artemisia (Artemisia asiatica, Artemisia capillaris, Artemisia rupestris, Artemisia scoparia, Artemisia vestita)
- Reduces microbial respiratory pathogens in vivo and in vitro – D/E (41)(118)(119)
- Increases humoral & cellular immune response to influenza vaccination in vivo – D (125)
- Reduces influenza A replication in vitro – E (68)(117)(126)
- Traditionally used to prevent or treat pathogenic infections due to its species-wide anti-bacterial and anti-viral properties, with special applications in malaria – F (51)
Licorice (Glycyrrhiza glabra, Glycyrrhiza inflata, Glycyrrhiza uralensis)
- Increases humoral & cellular immune response to influenza vaccination in vivo – D (1)
- Increases protection against influenza inoculation, or INF-γ production from T cells, & inhibition of neuraminidase (viral replication enzyme) in response to influenza virus in vivo and in vitro D/E (14)(33)(56)(93)(106)(111)
- Reduces human respiratory syncytial virus mainly via inoculation prevention. If inoculated, may stimulate INF-β for viral inhibition in vitro – E (19)(26)(109)
- Exhibits broad anti-viral properties against herpes, HIV, hepatitis, and influenza viruses – F (74)
- Traditionally used in many diseases including respiratory disorders due to its anti-microbial and anti-parasitic properties – F (21)
- Reduces prevalence of A/H1N1 virus influenza, the frequency of influenza-like symptomatic episodes, symptom severity, and duration of infection – B (15)
Propolis (Apis mellifera)
- Reduces presence of viral microflora in upper airways – D (11)
- Increases survival via influenza clearance from induction of TNF-related apoptosis-inducing ligand (TRAIL) mRNA in vivo – D (101)
- Reduces influenza hemagglutinin mRNA in vivo and in vitro – D/E (86)(101)(105)
- Reduces influenza presence in bronchoalveolar lavage fluid similarly to oseltamivir in vivo – D (89)
- Broad anti-bacterial activity for S. aureus, methicillin-resistant S. aureus, S. pyogenes, S. pneumoniae, H. influenzae, Enterococcus spp., E. coli, P. mirabilis, & P. aeruginosa, and broad anti-viral activity against adenovirus, influenza, parainfluenza, & herpes type 1 viruses in vitro – E (20)(31)
- Traditionally used for its anti-infectious and anti-inflammatory properties – F (7)
The following ingredients may be used in applications related to the improvement of breathing (lung function), particularly induced by airway spasms or constriction.
Elecampane (Inula helenium, Inula japonica)
- Reduces NF-κB, ERK, and Akt pathway to reduce pro-inflammatory cytokines TNF-α, IL-1β, & IL-6, and consequential lung injury (lung edema, thickening of the alveolar wall, and inflammatory cell infiltration) in vivo; activates Nrf2 pathway – D (18)(122)
- Reduces IgE & Th2 cytokines counts and infiltration in bronchoalveolar lavage fluid, airway hyperresponsiveness, and mucus hypersecretion in asthma in vivo – D (71)
- Traditionally used in respiratory conditions such as bronchitis and cough caused by inflammation or bacteria – F (85)
Eucalyptus (Eucalyptus globulus)
- Increases lung function – B (112)(113)
- Reduces shortness of breath, & exacerbation frequency/severity in asthma or COPD – B (112)(113)
- Reduces need for adjunct glucocorticosteroids – C (45)
- Reduces bronchiolitis severity, mucin hypersecretion, and inflammatory cell infiltration bronchoalveolar fluid in vivo – D (58)
- Traditionally used in the improvement of airway function by relaxing respiratory muscles and to cause expulsion of mucus – F (17)
Horehound (Marrubium vulgare)
Hyssop (Hyssopus officinalis, Hyssopus cuspidatus)
- Reduces leukotriene secretion to halt bronchoconstriction in vivo – D (27)
- Modulates transcription for Th1, Th2 and Th17 differentiation in asthmatic inflammation in vivo – D (108)
- Traditionally used to treat asthma – F (44)
Ivy (Hedera helix)
- Increases respiratory function in bronchial asthma particularly as adjunctive therapy – A (38)(124)
- Reduces bronchitis symptoms severity – B (12)(24)(80)(82)
- Traditionally used in conditions of the respiratory tract with properties that relax airway musculature and expel mucus – F (92)
Lobelia (Lobelia inflata)
- Traditionally used to promote pulmonary ventilation and used in respiratory disorders. May favor use as an expectorant in the presence of mucus hypersecretion. Note: High doses can produce cough – F (97)
Thyme (Thymus vulgaris)
- Reduces bronchitis symptoms severity in use with other herbal combinations such as ivy, thyme, and primrose – B (42)(35)(48)(59)(62)
- Increases B2-adrenergic receptor stimulation to cause airway relaxation in vivo – D (87)
- Traditionally used in many applications of respiratory disorders of the bronchi, asthma, coughing and mucus expulsion – F (77)
Yarrow (Achillea millefolium)
- Increases airway relaxation via B2-adrenergic receptor stimulation, calcium-channel or histamine receptor blockades, or inhibition of muscarinic receptors in vivo and in vitro – D/E (4)(25)(49)(52)(87)
- Traditionally used in respiratory disorders through bronchodilation and anti-inflammatory properties – F (2)
The following ingredients may be used in applications related to reduce or prevent coughing.
Black cherry (Prunus serotina)
- Traditionally used to treat cough – F (30)
Ivy (Hedera helix)
- Reduces URTI symptoms, particularly cough – A (12)(24)(39)(80)(82)(84)
- Traditionally used in conditions of the respiratory tract particularly with cough – F (92)
Tussilago (Tussilago Farfara)
- Reduces cough with additional expectorant and anti-inflammatory properties in vivo – D (55)(115)(120)
- Traditionally used to treat cough in respiratory conditions – F (53)
The following ingredients may be used in applications related to relieving inflamed mucus membranes via coverage with polysaccharide-rich substances.
Licorice (Glycyrrhiza glabra)
- Traditionally used as a demulcent with possible stimulatory actions on tracheal mucous secretion – F (13)
Marshmallow (Althaea officinalis)
- Reduces dry, ACE inhibitor-induced cough – B (76)
- Reduces cough reflex in vivo – D (98)(99)
- Increases bioadhesive layers to promote cell vitality and proliferation in healing of irritated mucous membranes in vitro – E (16)
- Traditionally used for its polysaccharides that soothe irritated mucous membranes, and reduce cough – F (60)
Plantago (Plantago lanceolata, Plantago major)
- Plantago polysaccharides show adhesion to epithelial tissues ex vivo, which may contribute to its demulcent actions on irritated mucous membranes – D (83)
- Traditionally used to soothe throat inflammation; demulcent effects demonstrated in the GI tract might generalize to tissues of the airway – F (23)(78)
Slippery elm (Ulmus rubra)
- Traditionally used for its polysaccharides that soothe mucosal inflammation and alleviate sensations signaling the need to cough – F (110)
The following ingredients may be used in applications related to the induction of perspiration.
Boneset (Eupatorium perfoliatum)
- Traditionally used as a diaphoretic in the treatment of fever and colds – F (37)
Ginger (Zingiber officinale)
- Traditionally used as a diaphoretic to eliminate colds – F (88)
The following ingredients may be used in applications related to the removal of hypersecretions of mucus.
Horehound (Marrubium vulgare)
- Traditionally used as an expectorant – F (75)
Mullein (Verbascum thapsus)
- Traditionally used for its properties as an expectorant to provide relief in respiratory conditions – F (104)
- Increases prevention of airway obstruction and inflammation in chronic bronchitis or COPD – A (9)
- Reduces symptoms including cough, sputum, labored breathing – A (9)(32)(95)
Thyme (Thymus vulgaris)
- Reduces bronchitis symptoms severity when used in combination with other herbs such as ivy, thyme, and primrose – B (42)(35)(48)(59)(62)
- Reduces hypersecretion of mucus by reducing the secretion of mucin 5AC proteins and inflammation in combination with primula in vivo and in vitro – D/E (67)(90)
- Traditionally used to improve mucus expulsion in asthma, cough and respiratory conditions of the bronchi – F (77)
The following ingredients may be used in applications related to the reduction of fever.
Andrographis (Andrographis paniculata)
- Reduces body temperatures and fever in patients with upper respiratory tract infections, such as pharyngotonsillitis – B (28)(79)(103)
- Traditionally used to treat fever – F (10)(50)
Feverfew (Tanacetum parthenium)
- Traditionally used to treat fever – F (69)
Honeysuckle (Lonicera japonica)
- Reduce internal temperature in vivo – D (29)(57)
- Traditionally used to treat fever via its anti-inflammatory effects – F (54)
The bottom line
In addition to the more common natural ingredients that provide immune support like echinacea, elderberry, vitamin C, vitamin D, and zinc, there are numerous alternative immune-modulating and respiratory system support ingredients that practitioners and patients can consider.
These ingredients may be used as a means to counteract pathogens like bacteria and viruses, or in the treatment of respiratory symptoms and more serious respiratory conditions related to pathogenic infection.
Note: this reference document and the associated infographic will continue to evolve, so check back often for updates.
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