The Best Approach to COVID Prevention? It’s Not Up Your Nose
Nasal sprays aren’t part of a science-based multilayered COVID-prevention strategy
Disclaimer: The following is general information provided for public health educational purposes and is not intended as individual medical advice. If you have individual medical questions, please consult your personal doctor or healthcare provider.
When it comes to COVID precautions, it’s best to incorporate a multilayered approach, including masking, improving air ventilation and filtration, getting the latest available vaccines, physical distancing, and testing. Using as many proven layers of protection as you can at once reduces the risk of COVID exposure and harmful consequences.
Members of our community often ask me whether there is anything else beyond these multilayered precautions that I am doing to prevent COVID infection. The short answer is “no,” and I’ve put this post together to answer some common questions and explain my approach. I do not use or recommend unproven COVID prevention approaches, including nasal sprays, mouth washes, eye drops, and supplements. Currently, none of these approaches are FDA-approved for COVID prevention. See this Ars Technica article for an overview on FDA and Federal Trade Commission actions against companies marketing COVID nasal products.
This post is limited to a US-based perspective, recognizing that issues involving international regulations may differ and are outside of my experience. In the US, the FDA (Food and Drug Administration) is the best authority for vetting drugs and medical devices. Understandably, the lack of a strong public health response in the ongoing pandemic has led to some public mistrust in government authorities. Although the FDA is not infallible, there is no other authority in the US that has the infrastructure, funding, and expertise to evaluate a drug or medical device for its potential risks and benefits on the basis of research studies and clinical trials.
For me to consider a nasal spray, mouth wash, eye drop, or other drug to be proven, at minimum it needs FDA approval or authorization. It’s important to note that “unproven” does not necessarily mean that the product does not work, but rather that there is insufficient evidence to support the use of a product for a particular application.
Unproven COVID products do not just have a lack of proven benefits—they can cause harm
You may encounter unproven products for COVID prevention or treatment on social media, available over the counter at pharmacies, from online vendors, and in the peer-reviewed research literature (such as PubMed). Unproven products can seem attractive, especially when social media marketing overhypes potential benefits, without mention of risks or uncertainties. Even for people who are highly informed about COVID, it is easy to be swayed by aggressive advertising and personal anecdotes about unproven products.
Unproven methods for COVID prevention can cause harm in at least three ways:
1. Direct harm from the product itself. Unproven approaches may have insufficient information available about potential risks. Some products may have known risks, although those risks may not be included in advertisements or promotions of those products.
2. Indirect harm due to creating a false sense of security, such that effective precautions aren’t taken. For example, someone may attend a social gathering maskless because they are using an unproven nasal spray, resulting in unnecessary exposure to COVID.
3. Financial harm due to money spent on a potentially ineffective or harmful product. Money is best spent on proven COVID prevention approaches.
What are some appropriate uses of nasal sprays, mouth washes, and eye drops?
Nasal sprays can be used for a variety of common medical conditions, such as allergies, upper respiratory infections (colds), and sinus infections. Although many nasal sprays may be available over the counter, getting medical advice is important for using nasal sprays appropriately as well as for diagnosing and treating the underlying condition that might be causing nasal symptoms.
Saline nasal sprays and rinses, such as neti pots, are commonly used to relieve dry nasal passages and reduce symptoms from allergies and upper respiratory infections. Saline does not include a medication or active ingredient. To avoid the risk of amoeba infection, sterile or distilled water should be used to make saline, or clean drinking water can be boiled according to the instructions given by the CDC and left to cool before using it to make saline.
Mouthwashes may be used for preventing gingivitis (gum inflammation), preventing tooth decay, and reducing bad breath. Eye drops may be used for a variety of eye conditions, including dry eye, infections, and glaucoma.
For all of these products, consulting an appropriate medical professional with any questions or concerns is recommended.
How can I identify unproven COVID prevention products?
Spotting unproven products can be difficult, and when in doubt you should check with a trusted individual or personal medical provider. Here are a few warning signs you can keep an eye out for:
1. Claims that seem exaggerated, such as nasal sprays that claim they kill 99.99% of viruses or block all infectious agents
2. Products that can only be purchased from international sources
3. Vendors that do not take standard payment methods, for example not taking credit cards but only accepting checks or wire transfers
4. Vendors that sell prescription medications without requiring a prescription from your doctor or healthcare provider
5. US pharmacies that do not employ a state-licensed pharmacist
6. Social media marketing tactics such as referral codes, personal testimonials, and exclusive webinars within COVID-cautious groups
7. Endorsement by individuals, institutions, or groups that eschew proven protection methods, including those that make anti-mask or anti-vaccination statements
8. Claims that products are drug-free, all natural, homeopathic, contain essential oils, or are chemical-free
Notably, enforcement of regulations is not perfect. Just because a product is available for sale does not mean the product is safe or FDA-approved.
Nose, Mouth, and Eye-Based Approaches Are Biologically Unlikely to Work for COVID Prevention
COVID spreads through the air via respiratory aerosols,1 which are tiny and enter the smallest spaces deep within our lungs, the alveoli. The cells of the alveoli contain the biological machinery for COVID infection, as do many other cell types throughout the body.2
Nasal sprays, mouth washes, and eye drops will primarily act in the area where they are applied and would be unlikely to affect tissue deep within the lungs. As a contrast to nasal sprays that produce large droplets, inhalers used for administration of lung medications for chronic lung diseases such as asthma produce aerosols that are designed to produce smaller aerosol particles.3 Just as the aerosols generated by an inhaler penetrate deeply into the lungs, the small particles of infectious aerosols can bypass the nasal lining and enter the alveoli. Also, the surface area of the nasal lining4 is significantly smaller than the internal surface area of the lungs.5,** Thus, products applied to the nose or mouth are unlikely to even be present everywhere in the respiratory tract that COVID infection can occur.
To think about it another way, in the setting of exposure to dangers like wildfire smoke particulates (PM2.5) or asbestos, it sounds silly to suggest that using a nasal spray before or after exposure might reduce the need for a mask. Similarly, it’s not believable that nasal sprays would provide sufficient protection against COVID.
Given the uncertainties around nasal sprays and other products, it is vitally important to continue to use proven, multilayered approaches, including advocating for masking in healthcare and dental settings where patients may need to unmask in order to receive care.
Treatment versus Prevention Claims must be Considered Separately in Evaluating Research
It is important to separate claims of prevention versus treatment in understanding how research studies fit into the bigger picture. Research studies need to be planned to study either treatment or prevention, usually not both. Findings from a study on treatment of a disease do not mean that the same intervention may be helpful for prevention of that disease. Risks also are evaluated differently for preventative measures versus treatment for a known disease.
Interventions aimed at prevention are often given to large groups of people who do not yet have a particular disease but are at risk of developing that disease. The risks of disease and potential for severe outcomes are measured at a group or population scale and are often relatively low. The disease and outcome prevalence might be measured per thousand, ten-thousand, or hundred-thousand people. Thus, in order to be appropriately adopted in public health or medical practice, preventative approaches usually need to pose very low risk to the individual.
Treatment, in contrast, is usually given to a patient who has a confirmed diagnosis of a disease, and there are often clear dangers to the patient if the disease is left untreated. Risks of side effects or adverse events may be an appropriate tradeoff when the benefits of the treatment are significant. Medical decision-making is made by a discussion between the patient and their doctor or healthcare provider.
As an example, chemotherapy is used to treat cancer but it is not generally used to prevent it. Chemotherapy has severe side effects that are often considered acceptable for patients who currently have cancer, because the chemotherapy treats their cancer and can prolong their life, improve their quality of life, or even cause remission. In patients without cancer, chemotherapy would pose unacceptable risks without a clear benefit.
When a study indicates a potential benefit for a drug in active COVID infections, that does not mean the same drug would be appropriate for COVID prevention.
Examples of Unproven Nasal Prevention Approaches
Nitric oxide: One nasal spray that is commonly marketed with misleading claims on social media (a nitric oxide nasal spray) has clinical trials registered with the FDA. As of this writing on 4/28/2024, none of the studies listed had results posted on the FDA’s clinical trial records. A 2022 study of this nitric oxide nasal spray was funded by the pharmaceutical company, and following initial publication, a correction indicated that the pharmaceutical company was involved in the data analysis, writing of the manuscript, and decision to publish.6 This casts some uncertainty on the validity of the results.
Antibiotic ointment: An early research study on nasal application of an over-the-counter antibiotic ointment has received extensive and misleading press exposure.7 Importantly, neomycin/polymyxin/bacitracin (brand name Neosporin) ointment is only intended for skin use and not for nasal use.
Quote from the MedlinePlus page on Neomycin, Polymyxin, and Bacitracin Topical:
This medication is for use only on the skin. Do not let neomycin, polymyxin, and bacitracin combination get into your eyes, nose, or mouth and do not swallow it.
Vaseline and petrolatum-based products (such as Neosporin) carry a risk of development of a type of severe lung damage called lipoid pneumonia if they are used inside the nose, as the nose drains down the throat and drainage can sometimes be aspirated into the lungs.
Colloidal silver: Although colloidal silver is not proven to treat or prevent any medical condition, a zine promoting colloidal silver nasal spray has been widely promoted on social media. Colloidal silver is particularly concerning because it can cause permanent blue-gray discoloration of the skin, poor absorption of important medications, as well as potential damage to the liver, kidneys, and brain. (Note: When a nasal spray is used, it eventually drains down the back of the throat and can be swallowed. Any product that is administered as a nasal spray is likely to enter the gastrointestinal tract as well.)
Quote from the NIH’s National Center for Complementary and Integrative Health:
The U.S. Food and Drug Administration (FDA) has warned that colloidal silver isn’t safe or effective for treating any disease or condition. … Silver has no known functions or benefits in the body when taken by mouth, and it is not an essential mineral.
Multilayered Proven Precautions Aid COVID Research, Now and For the Future
As a scientist, I love learning about amazing research advancements. Unfortunately, communication about research sometimes gets ahead of the facts. It also seems that as long as COVID continues to spread, so will pandemic grifting. That means that all of us need to be extra careful to engage with new information critically and to check with people we trust when something just doesn’t sound right. I certainly hope that research in the coming years will bring about new advances for COVID and Long COVID prevention, treatment, and diagnosis, but these discoveries are not likely to negate the need to prevent the spread of COVID.
Using and advocating for masking and other proven precautions today can reduce development of new variants, allowing COVID research to stay relevant longer, while saving lives and preventing unnecessary disablement. 😷
** A fun side note, the lungs are a biological approximation of a mathematical shape called a “fractal” in that the sac-like structures within the lungs are recapitulated at several scales. The resulting branching structures leading to smaller and smaller divisions and ultimately culminating in the alveoli, where gas exchange occurs, allowing carbon dioxide to leave and oxygen to enter red blood cells. This arrangement allows the lungs to have a very large surface area for gas exchange with thin walls between the air space and the blood vessels, contained within a relatively small volume within our chests. See this Fractal Foundation page for visuals and further explanation.
References
1. Wang CC, Prather KA, Sznitman J, et al. Airborne transmission of respiratory viruses. Science. 2021;373(6558):eabd9149. doi:10.1126/science.abd9149
2. Muus C, Luecken MD, Eraslan G, et al. Single-cell meta-analysis of SARS-CoV-2 entry genes across tissues and demographics. Nat Med. 2021;27(3):546-+. doi:10.1038/s41591-020-01227-z
3. Darquenne C. Aerosol Deposition in Health and Disease. J Aerosol Med Pulm Drug Deliv. 2012;25(3):140-147. doi:10.1089/jamp.2011.0916
4. Gizurarson S. Anatomical and Histological Factors Affecting Intranasal Drug and Vaccine Delivery. Curr Drug Deliv. 2012;9(6):566-582. doi:10.2174/156720112803529828
5. Fröhlich E, Mercuri A, Wu S, Salar-Behzadi S. Measurements of Deposition, Lung Surface Area and Lung Fluid for Simulation of Inhaled Compounds. Front Pharmacol. 2016;7:181. doi:10.3389/fphar.2016.00181
6. Tandon M, Wu W, Moore K, et al. Correction to “SARS-CoV-2 accelerated clearance using a novel nitric oxide nasal spray (NONS) treatment: A randomized trial.” The Lancet Regional Health - Southeast Asia. 2022;7:100110. doi:10.1016/j.lansea.2022.100110
7. Mao T, Kim J, Peña-Hernández MA, et al. Intranasal neomycin evokes broad-spectrum antiviral immunity in the upper respiratory tract. Proceedings of the National Academy of Sciences. 2024;121(18):e2319566121. doi:10.1073/pnas.2319566121
Could you please address the efficacy of saline sinus irrigation after potential exposure?
Thanks very much.