In search of the infallible cold remedy: ‘There are no antivirals, we only treat the symptoms’

An adult suffers between two and four colds a year; children, six to eight. These mild upper respiratory tract infections (they mainly affect the nose and throat), whose predominant symptoms are mucus, sneezing and nasal congestion, are common and generally low-risk, but very annoying. So much so that when the first symptoms appear, people persistently look for infallible remedies, either at home or at the drugstore. But an effective therapeutic treatment to neutralize or prevent colds has not yet been found. For now, there is only solid evidence for drugs and lifestyle recommendations to cope with the symptoms as best as possible. “There are no treatments that destroy the cold virus. Antibiotics are useless and there are no antivirals. We can only treat the symptoms,” explains José María Molero, coordinator of the Infectious Diseases Working Group of the Spanish Society of Family and Community Medicine.

Behind the runny nose and congestion that herald a cold, there may be more than 200 different viral strains. Microorganisms from the family of rhinoviruses, adenoviruses and coronaviruses (other than Sars-Cov-2) are the usual suspects, so antibiotics are not an option (these drugs are used for bacterial, not viral, infections). There are also no preventive vaccines: “They were halted because of their low efficacy. Making a vaccine for dozens of serotypes is very difficult,” Molero admits.

The treatment is symptomatic, both for adults and children, insists Carlos Martín de Vicente, a pediatric pulmonologist at Miguel Servet Hospital in Zaragoza and member of the Spanish Society of Pulmonology and Thoracic Surgery: “There is no medication that can shorten the infection and there is no prevention, except for the measures we had to apply with Covid [interpersonal distancing, hand-washing and wearing a mask].” The scientific community, however, has not given up and continues to search for therapeutic alternatives to combat colds.

A review by Cochrane, the independent network of researchers that analyses scientific evidence, suggested a few months ago that zinc (in the form of lozenges, nasal sprays and syrup) might reduce the duration of a cold from seven to five days, although the evidence was very limited. The theory is that this mineral may have the ability to interfere with the replication of the virus when it comes into contact with viral particles in the nose, mouth and throat. However, the authors of the analysis emphasized that “our confidence in the evidence is mostly low to very low,” and warned that “due to the large differences between studies in the approaches used to test the effectiveness of zinc, it is likely that additional studies are required before any firm conclusions can be drawn.”

“Those considering zinc as a treatment for colds should be aware of the limited evidence base and potential side effects [bowel problems, nausea and unpleasant taste],” warns Daryl Nault, a professor of Integrative Health at the University of Maryland and an author of the review. In a comment to the Science Media Center, Harri Hemilä, a researcher at the Department of Public Health at the University of Helsinki and an expert in the study of zinc in the cold, said that zinc is effective and criticized the Cochrane review for not taking into account dosage or type of pill: “The review does not separate lozenges [that dissolve in the mouth] from regular tablets, which is an obvious error. Studies with lozenges have shown benefit, but studies with ordinary tablets have not,” he added.

The U.S. National Institutes of Health also notes that results of clinical trials with zinc supplements have been “inconsistent,” but, “overall, supplemental zinc in lozenge or syrup form appears to reduce the duration, but not the severity, of signs and symptoms of the common cold when taken soon after a person develops a cold.”

Garlic and probiotics

This is not the first time the Cochrane network has reviewed evidence on potential remedies for the common cold. Another study in 2020 concluded that there was not enough evidence to confirm that garlic, which is credited with antimicrobial and antiviral properties, can prevent or treat colds. On the effect of Echinacea plant preparations, another Cochrane review from 2013 also expressed caution about their potential benefits: the authors warned that consumers need to be aware that products under this name differ widely and most have not been tested in clinical trials. The research found “hints” of potential benefits in adults, but the evidence for the effects was weak: “In general, trials investigating Echinacea for preventing colds did not show statistically significant reductions in illness occurrence. However, nearly all prevention trials pointed in the direction of small preventive effects.” The American Association of Family Physicians (AAFP) considers that it is no more effective than placebo in reducing the duration or severity of symptoms.

Cochrane researchers also analyzed the evidence on the role of probiotics against the common cold and concluded that they “could be beneficial”, but here too more in-depth research is needed to fine-tune the extent of their effect: according to the authors, these products, which are made up of live micro-organisms that help maintain the balance of the intestinal microbiome, could reduce the number of people diagnosed with three such infections by 41% and may have the capacity to reduce the duration of these episodes by just over a day. However, the level of certainty of all these conclusions is limited, they warned.

Regarding vitamin C, the Mayo Clinic warns that this supplement has not been shown to help prevent colds, but it does admit that “some studies have shown that taking vitamin C before cold symptoms begin may shorten the duration of symptoms.” The American Association of Family Physicians, however, rates vitamin C supplements as “no more effective than placebo” in reducing the duration of symptoms or severity in adults (in children, they do see a small effect on the duration of symptoms).

What does work to alleviate — but not shorten — the symptoms of a cold in adults, says Molero, are acetaminophen, ibuprofen, and combinations of antihistamines and decongestants. And staying well hydrated also helps. “All of this helps to reduce symptoms, but it doesn’t cure the cold any sooner. Vapors, for example, alleviate nasal and throat symptoms, but they don’t shorten the duration of the cold,” she adds. Honey also helps, in adults and in children over one year of age, to relieve coughing (in babies under 12 months it is not recommended due to the risk of botulism).

Children’s colds “go away on their own”

When it comes to childhood colds, the AAFP does conclude that analgesics are effective symptomatic treatments for fever-related discomfort and the mucolytic acetylcysteine can reduce coughing in children aged two or older, but it does not recommend any medication for children under four years of age. The Spanish Association of Pediatrics also does not recommend giving cold medicines to very young children (only antipyretics if the fever bothers them a lot) and warns that most of these drugs are not, in fact, authorized for use in children under two years of age. “Colds go away on their own,” insists the scientific society.

Carlos Rodrigo, clinical director of Pediatrics at the Germans Trias i Pujol Hospital in Badalona, says that “there is nothing that can be done” for the common cold in children. The doctor admits that, although sometimes these symptoms “can be the beginning of something else”, such as the flu, Covid or bronchiolitis caused by the respiratory syncytial virus, in most cases it is a trivial and unworrisome process. “It is so trivial that the child is becoming immune. It is not awarded more importance because it is a benign infection. It is annoying, but nothing more,” he says.

The experts do agree that nasal irrigation with saline solution relieves nasal congestion. “There has been a lot of hype about nasal irrigation. Saline solution, which is water with salt at very low concentrations, is used to help dissolve mucus. It does not cure or prevent infections, but it does clean and unclog,” says Rodrigo.

In this regard, at the European Respiratory Society Congress held in September, a group of British researchers presented the results of a study suggesting that a hypertonic saline solution administered through nasal drops can reduce the duration of colds in children. “We found that children using salt-water nose drops had cold symptoms for an average of six days where those with usual care had symptoms for eight days. The children receiving salt water nose drops also needed fewer medicines during their illness,” explained Steve Cunningham, from the University of Edinburgh, in a statement from the scientific society.

“Salt is made up of sodium and chloride. Chloride is used by the cells lining the nose and windpipes to produce hypochlorous acid within cells, which they use to defend against virus infection. By giving extra chloride to the lining cells this helps the cells produce more hypochlorous acid, which helps suppress viral replication, reducing the length of the virus infection, and therefore the duration of symptoms,” he explained. The study, however, has not yet been published in any scientific journal.

Martín de Vicente agrees, with all due caution and while waiting to learn more and validate the data in other research, that it is a “quite interesting and promising” study: “It is cheap and provides a possible preventive benefit because those who used it had a lower frequency of wheezing. It could be a protective agent for possible complications such as bronchitis,” he says. Rodrigo, for his part, considers that it is a “solid” research group, but is cautious: “Instead of using saline solution, they have used a higher concentration of salt to help dissolve the mucus. But I still find it surprising that it reduces the duration of the cold and the contagiousness. It is not known that saline solution and saline solutions have an antiviral effect.”

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