Flu (influenza)

What doctors say*

* Official guidelines from NICE, NHS and other medical authorities.

Should antibiotics be used? >

No. Flu and other viral infections do not respond to antibiotics, unless there are secondary bacterial complications.

Likely duration if untreated >

A week or so – with recovery often taking longer.

Conventional self-care advice >

  • Rest and sleep – allowing time off for proper recovery
  • Keep warm
  • Drink adequate fluids

Opportunities for antibiotic alternatives >

In almost all cases

 

See also

Note: to help get over the flu it is worth also considering remedies on the Common cold page. Both conditions could be improved by helping the body defend itself against viruses. Check also the general advice on the Fever page to manage this common aspect of flu.

Andrographis
> what do these ratings mean?

There is clinical evidence that andrographis can shorten the duration of upper respiratory infections compared with placebo. Andrographis is best used as a supplement. It is wise to choose a reputable supplier rather than buy indiscriminately on the internet.

See the evidence ...

An analysis of two systematic reviews and eight clinical trials concluded that there was qualified evidence that andrographis was useful in the treatment of upper respiratory tract infections [Kligler, 2006].

A more recent randomised controlled trial assessed changes in symptom scores among 223 patients with uncomplicated upper respiratory tract infection. In treatment with a proprietary andrographis or placebo, mean scores of all symptoms showed a decreasing trend from day 1 to day 3 but from day 3 to day 5 most of the symptoms in placebo group either remained unchanged or worsened whereas in andrographis group all symptoms showed a decreasing trend [Saxena, 2010].

References

Kligler B, Ulbricht C, Basch E, Kirkwood CD, et al (2006). Andrographis paniculata for the treatment of upper respiratory infection: a systematic review by the natural standard research collaboration. Explore (NY) 2(1): 25-9

Link to Abstract

Saxena RC, Singh R, Kumar P, Yadav SC et al (2010).  A randomized double blind placebo controlled clinical evaluation of extract of Andrographis paniculate (KalmCold™) in patients with uncomplicated upper respiratory tract infection. Phytomedicine 17, 3–4, 178-185

Link to Abstract

Mushroom supplements
> what do these ratings mean?

There is increasing clinical trial evidence that mushroom supplements (containing β-glucans and other immunoactive constituents) reduce the incidence and severity of respiratory tract infections. The main species studied are reishi (ganoderma), shiitake, and maitake mushrooms. Yeast supplements may also be considered and are generally more available.

It is wise to choose a reputable supplier rather than buy indiscriminately on the internet.

In theory some of the benefits of supplements may be obtained by eating a range of mushrooms in the diet. However there is no direct evidence for this.

See the evidence ...

Mushrooms contain biologically active polysaccharides (e.g., β-glucans) which demonstrate immunomodulatory activity in a number of test models, engaging several key receptors on immune cells. Although not absorbed into the body they may engage with gut surface immune cell receptors and there is evidence that these activate systemic non-specific immune responses [Richter, 2014; Vetvicka, 2013]. They also generate appreciable levels of vitamin D under the influence of UV in sunlight (see separate reference below). There are a number of placebo-controlled clinical trials that demonstrate that mushroom supplements do reduce the incidence and severity of respiratory tract infections [eg. Graubaum, 2012; Talbott, 2012; Fuller, 2012].

References

Fuller R., Butt H., Noakes P.S., et al (2012). Influence of yeast-derived 1,3/1,6 glucopolysaccharide on circulating cytokines and chemokines with respect to upper respiratory tract infections. Nutrition. 28: 665–669

Link to Abstract

Graubaum H.J., Busch R., Stier H., Gruenwald J. (2012)  A double-blind, randomized, placebo-controlled nutritional study using an insoluble yeast beta-glucan to improve the immune defence system. Food Nutr. Sci.;3: 738–746

Link to Full Text

Richter J., Svozil V., Kral V., et al. (2014) Clinical trials of yeast-derived β-(1,3) glucan in children: Effects on innate immunity. Ann. Transl. Med. 2: 15

Link to Abstract and Full Text

Talbott S.M., Talbott J.A. (2012) Baker’s yeast beta-glucan supplement reduces upper respiratory symptoms and improved mood state in stressed women. J. Am. Coll. Nutr. 31: 295–300

Link to Abstract

Vetvicka V., Richter J., Svozil V., et al (2013). Placebo-driven clinical trials of yeast-derived β-(1,3) glucan in children with chronic respiratory problems. Ann. Transl. Med. 1: 26

Link to Abstract and Full Text

Plant polyphenols
> what do these ratings mean?

Polyphenols, such as flavonoids and anthocyanidins, are very common constituents of plants, fruit and vegetables, especially those that are coloured.  Supplementation with polyphenols has been shown to shorten the duration of colds and viral infections. High natural sources of polyphenols are red grapes (and red wine), cocoa, and pomegranate.

See the evidence ...

In a systematic review and meta-analysis to assess the efficacy of dietary flavonoids on upper respiratory tract infections (URTIs) and immune function in healthy adults, fourteen studies were included and the primary outcome measure was the effect of flavonoids on URTI incidence, duration, and severity. Of the included studies, flavonoid supplementation ranged from 0.2 to 1.2 g/d. Overall, flavonoid supplementation decreased URTI incidence by a third compared with control, with no apparent adverse effects. Sick-day count was decreased by 40% with flavonoid supplementation. The conclusions were that flavonoids could be a viable supplement to decrease URTI incidence in an otherwise healthy population [Somerville, 2016].

References

Somerville VS, Braakhuis AJ, Hopkins WG. (2016) Effect of Flavonoids on Upper Respiratory Tract Infections and Immune Function: A Systematic Review and Meta-Analysis. Adv Nutr. 7(3): 488-97

Link to Abstract and Full Text

Probiotics
> what do these ratings mean?

In research studies of mixed quality, various probiotic supplements, especially containing strains of Lactobacillus and Bifidobacteria, have been shown to reduce the frequency, duration and intensity of respiratory infections, especially in children.

All these benefits were seen after at least several weeks consumption of these probiotics and it is less likely that short term use will have much impact. Probiotics may therefore best be seen as preventative rather than as treatments.

See the evidence ...

 

A meta-analysis of the clinical research literature [Wang, 2016] has shown that the consumption of probiotics reduced the number of subjects with at least one episode of respiratory tract infections; furthermore, children supplemented with probiotics showed the number of days with fever and number of days of absence from the day care/school were lower than in children who were given a placebo. However, there was no significant difference in overall disease duration.

A Cochrane analysis [Hao, 2015] showed that probiotics were better than placebo in reducing

  1. the number of children, adults and the elderly who had episodes of acute infection of the upper respiratory tract,
  2. the average episode length of acute infection of the upper respiratory tract, and
  3. the use of antibiotics and the number of days school/work off.

However, the quality of this evidence was low or very low.

In a more recent Cochrane review [Scott, 2019] probiotics decreased the proportion of children taking antibiotics for any infection.

Another review focused on three probiotic strains (Lactobacillus gasseri, Bifidobacterium bifidum and Bifidobacterium longum) [Kalyuzhin, 2016]. This included two randomised double-blind studies by one research group: in the first [de Vrese, 2005] the intake of these bacteria for 3 months or more shortened common cold episodes by almost 2 days and reduced the severity of symptoms. In the second [de Vrese, 2006], the intake of Bifidobacteria and Lactobacilli had no effect on the incidence of common cold infections, but again  shortened the duration of episodes by almost 2 days, and reduced the severity of symptoms and blood test measures.

A large prospective, randomized, double blind, placebo-controlled study on healthy volunteers was carried out over three winter seasons with strains of Lactobacillus and Bifidobacterium, taken with lactoferrin and various prebiotics. This study demonstrated that regular, long-term intake of these may reduce the incidence and severity of respiratory diseases during the cold season [Pregliasco, 2008].

A later large randomized double-blind, placebo-controlled trial showed that daily consumption of strain of Lactobacillus paracasei resulted in reduced duration of upper respiratory symptoms [Jespersen, 2015].

References

de Vrese M, Winkler P, Rautenberg P, et al (2005) Effect of Lactobacillus gasseri PA 16/8, Bifidobacterium longum SP 07/3, B. bifidum MF 20/5 on common cold episodes: a double blind, randomized, controlled trial. Clin Nutr. 24(4): 481-91

Link to Abstract

de Vrese M, Winkler P, Rautenberg P et al. (2006) Probiotic bacteria reduced duration and severity but not the incidence of common cold episodes in a double blind, randomized, controlled trial. Vaccine. 24(44-46): 6670-4

Link to Abstract

Jespersen L, Tarnow I, Eskesen D, et al (2015) Effect of Lactobacillus paracasei subsp. paracasei, L. casei 431 on immune response to influenza vaccination and upper respiratory tract infections in healthy adult volunteers: a randomized, double-blind, placebo-controlled, parallel-group study. Am J Clin Nutr.101(6): 1188-96

Link to Abstract

Kalyuzhin OV, Afanasyev SS, Bykov AS. (2016) [Probiotics as stimulators of immune response against pathogens in the respiratory tract]. Article in Russian. Ter Arkh. 2016;88(5):118-124

Link to Abstract

Pregliasco F, Anselmi G, Fonte L, et al (2008) A new chance of preventing winter diseases by the administration of synbiotic formulations. J Clin Gastroenterol. 42 Suppl 3 Pt 2: S224-33

Link to Abstract

Vitamin D
> what do these ratings mean?

There is good quality evidence that vitamin D supplements can reduce the risk of catching colds or other respiratory infections.

Regular dosing is more effective than taking the vitamin intermittently and benefits will be felt most by people who are depleted in the vitamin. However in Britain and other urban cultures and where there is less exposure to sunlight, vitamin D deficiency is quite common.

See the evidence ...

A rigorous systematic review and meta-analysis of randomised, double blind, placebo-controlled trials of supplementation with vitamin D3 or vitamin D2, identified 25 eligible trials (n=11,321). The body of evidence contributing to these analyses was assessed as being of high quality. Vitamin D supplementation reduced the risk of acute respiratory tract infection among all participants. Those receiving daily or weekly vitamin D were better protected than those taking intermittent doses, and protective effects were stronger in those with lowered baseline 25-hydroxyvitamin D levels [Martineau, 2017].

References

Martineau AR, Jolliffe DA, Hooper RL, et al. (2017) Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 356: i6583

Link to Abstract and Full Text

Elderberry
> what do these ratings mean?

In one clinical research study flu symptoms were relieved earlier in subjects taking elderberry syrup than those taking  placebo syrup.

Elderberry syrup and supplements are readily available. It is advised to choose products from reputable suppliers rather than indiscriminately over the internet.

It is also possible to make your own elderberry syrup at home by wildcrafting the berries from hedgerows in the autumn.

See the evidence ...

Sixty patients (aged 18-54 years) suffering from influenza-like symptoms for 48 h or less were enrolled in a randomized, double-blind, placebo-controlled study during the influenza season of 1999-2000 in Norway [Zakay-Rones, 2004]. Patients received 15 ml of elderberry or placebo syrup four times a day for 5 days, and recorded their symptoms using a visual analogue scale. Symptoms were relieved on average 4 days earlier and use of rescue medication was significantly less in those receiving elderberry extract compared with placebo. Elderberry extract seems to offer an efficient, safe and cost-effective treatment for influenza.

A randomized, double-blind placebo-controlled clinical trial of 312 economy class passengers travelling from Australia to an overseas destination aimed to investigate if a standardised membrane filtered elderberry extract has beneficial effects on physical, especially respiratory, and mental health. Measures were scored diary entries and surveys just before travel and at 4-days after travel. The placebo group participants had a significantly longer duration of cold episode days and the average symptom score was also significantly higher [Tiralongo, 2016].

References

Tiralongo E, Wee SS, Lea RA (2016) Elderberry Supplementation Reduces Cold Duration and Symptoms in Air-Travellers: A Randomized, Double-Blind Placebo-Controlled Clinical Trial. Nutrients. 8(4): 182

Link to Abstract and Full Text

Zakay-Rones Z, Thom E, Wollan T, Wadstein J. (2004) Randomized study of the efficacy and safety of oral elderberry extract in the treatment of influenza A and B virus infections. J Int Med Res 32 (2): 132-40

Link to Abstract

Exercise
> what do these ratings mean?

Although the evidence is mixed it appears that moderate levels of exercise can reduce the risk of catching respiratory infections.

Too much exercise is well known to expose athletes to more infections and too little appears to do the same.

See the evidence ...

A Cochrane review could not determine whether exercise is effective at altering the occurrence, severity or duration of acute respiratory infections. One analysis of four trials suggests that the number of days of illness per episode of infection might be reduced by moderate exercise. The small size of the studies, risk of bias and heterogeneous populations all contributed to the uncertainty. The authors concluded that larger studies, with less risk of bias from patient selection, blinding of outcomes assessors, reporting of all outcomes measured and with registration of study protocols, are required to settle the question. [Grande, 2015].

It is widely understood that intense exercise can increase susceptibility to upper respiratory infections. High exercise training workloads, competition events, and the associated physiological, metabolic, and psychological stress are linked with transient immune upsets, inflammation, oxidative stress, muscle damage, and increased illness risk. This evidence, combined with that pointing to benefits of moderate exercise have led to the development of the J-curve model (inwhich best protection is provided by levels of exercise between too much and too little) [Nieman, 2019].

 

References

Grande AJ, Keogh J, Hoffmann TC, Beller EM, Del Mar CB (2015) Exercise versus no exercise for the occurrence, severity and duration of acute respiratory infections. Cochrane Database Syst Rev CD010596

Link to Abstract and Full Text

Nieman DC, Wentz LM. (2019) The compelling link between physical activity and the body’s defense system. J Sport Health Sci. 8(3): 201-217

Link to Abstract and Full Text

Relaxation
> what do these ratings mean?

There is moderate evidence that reducing stress and improving relaxation will increase resistance to colds, flu and other respiratory infections.

Self-taught mindfulness, meditation, or simple hobbies and restful activities like gardening, fishing or raambling are likely to be as least as effective as formal classes in meditation, yoga or tai chi. The method is only as good as its application.

See the evidence ...

Evidence suggests that psychological, social and behavioural factors influence susceptibility to acute respiratory infections [Adam, 2013; Smith, 2013]. For example, people with higher emotional reactivity and vulnerability to stressful life events are at greater risk [Cohen, 2002].

In a randomized controlled prevention trial with three parallel groups among community-recruited adults who did not regularly exercise or meditate, there were marginal reductions in winter respiratory tract infections among those in both mindfulness-based stress reduction training and in moderate sustained exercise groups [Barrett, 2018].

References

Adam Y, Meinlschmidt G, Lieb R (2013) Associations between mental disorders and the common cold in adults: a population-based cross-sectional study. J Psychosom Res 74: 69–73

Link to Abstract

Barrett B, Hayney MS, Muller D, et al. (2018) Meditation or exercise for preventing acute respiratory infection (MEPARI-2): A randomized controlled trial. PLoS One. 13(6): e0197778

Link to Abstract and Full Text

Cohen S, Hamrick N, Rodriguez MS, et al (2002) Reactivity and vulnerability to stress-associated risk for upper respiratory illness. Psychosomatic Medicine 64: 302–310

Link to Abstract

Smith AP (2013) Twenty-five years of research on the behavioural malaise associated with influenza and the common cold.  Psychoneuroendocrinology 38: 744–751

Link to Abstract

Traditional home remedies worth trying

Spices

Consistent advice in managing feverish infections like flu is to keep you or the sufferer warm (though see also ‘Fever management’). At the first onset of chills it is natural and useful to take hot baths, have hot drinks and tuck into warm clothes or bed. It is also possible to add internal heating in other ways. The hot or warming spices such as cayenne, ginger and cinnamon are known to increase heat generation (‘thermogenesis’) and have long been used in fever management from ancient times.

There is a simple home remedy that provides all the benefits of spices in colds and flu. It is ginger and cinnamon tea. This tea will immediately counteract any symptom made worse by cold or improved by heat. It could be an actual cold, or a headache or pain that improves with a hot water bottle or hot bath. The tea triggers a reflex increase in blood flow to the mucous membranes of the mouth, airways and gut, and then elsewhere around the body.

As soon as you feel cold or the chills of a feverish infection coming on, take

  • one knob of fresh ginger (about the size of your thumb) freshly grated
  • a teaspoon of powdered cinnamon (best if freshly ground)

Add to a large mug and pour on boiling water. Stir, seep for 5 minutes or so, strain and sip. If this is helpful you may wish to make more and keep it in a vacuum flask for sipping through the day.

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Disclaimer

Knowledge and best practice in the health field are constantly changing.  Each person and illness is also unique and no general information can anticipate every circumstance, nor be appropriate for every reader. Each individual case is best assessed in person by a qualified health advisor.

In the case of remedies or other products, users should read the label carefully for detailed information about safe use and in the case of natural products should choose responsible manufacturers with independently assured quality standards and safety monitoring procedures.

To the fullest extent of the law, neither the College of Medicine nor the authors, contributors or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the materials herein.