Millions of people are diagnosed with sinusitis each year, for which they are prescribed antibiotics. Those with frequent sinus infections may wind up taking antibiotics repeatedly. However, there is a growing concern in the medical community that antibiotics, especially when taken frequently, may be causing harm.

Call it a case of unintended consequences.

Antibiotics are amazingly effective in treating infections caused by harmful bacteria. They can be a lifesaver. But antibiotics don’t just kill or inhibit the growth of harmful bacteria, they also kill good bacteria living in the body and this can lead to health problems. Bacteria can also develop antibiotic resistance.

While recent research is showing the harms of frequent use of antibiotics, especially to our microbiome, other exciting research is pointing a way forward. This is using beneficial bacteria (probiotics) to reduce or even eliminate the use of antibiotics for sinusitis and some other types of infections.

The antibiotic sinusitis cycle

We all have trillions of microbes (bacteria, viruses, fungi) living in communities within and on us, and this is the human microbiome. The sinus microbiome is similar – the community of hundreds of microbial species (bacteria, viruses, fungi) that normally live in the sinuses.

Sinusitis is a vicious cycle for many: take antibiotics for sinusitis and feel better, then during the next cold or sore throat sinusitis again develops, take antibiotics and again feel better. But over time we may find that the antibiotics don’t seem to be as effective, and annoying sinus symptoms can become constant, leading to chronic sinusitis.

When a person takes antibiotics, they kill or suppress both harmful and beneficial bacteria in the gut and sinuses. This undesirable effect on the sinuses was unknown until recently. For decades it was thought that the sinuses were sterile in healthy people, and that a sinus infection meant that harmful bacteria had invaded the sinuses. Antibiotics were a way of getting rid of the harmful bacteria.

But this turned out not to be the whole story.

Only recently with the development of new technology (genetic sequencing) it was discovered that a community of microbes live in healthy sinuses. The most surprising finding was that microbes that are considered beneficial and benign coexist with those that are generally viewed as harmful (pathogenic) in the sinuses. In healthy persons, all the species are in equilibrium with the beneficial bacteria keeping potentially harmful bacteria in check.

When antibiotics kill or suppress bacteria, it can result in an imbalance in the sinus microbial community and sinusitis symptoms. This is called dysbiosis. Disruption of the resident microbes in the sinuses can result in an overgrowth of harmful bacteria and increase susceptibility to infection, as well as cause sinusitis symptoms. In chronic sinusitis there is an imbalanced sinus microbiome and inflammation of the mucous lining of the sinuses.

Negative effects of antibiotics are long lasting

Disruption of the microbial community or dysbiosis can also be seen in the gut microbiome. Studies show that after taking antibiotics, bacterial species in the gut may take months to recover and some species may never come back. This means that the gut microbial community might look a little different (e.g., fewer species) after recovery.

The type of antibiotic taken is also important. While some antibiotics may just inhibit or suppress bacteria species that normally live in the gut, others actually kill them.

For example, one study found it took up to a year for gut bacteria to recover from a course of ciprofloxacin, while amoxicillin had no significant effect on gut microbial diversity. Another study in children found that the gut microbiota recovered within 6–12 months after a penicillin course, but did not fully recover from a macrolide (e.g., clarithromycin, azithromycin) course even after 2 years. A recent study found that tetracyclines and macrolides are especially devastating to normal gut bacteria. Doxycycline, erythromycin, and azithromycin killed several abundant gut microbial species, but just inhibited other species (which means they can bounce back after a time).

After a course of antibiotics, when some species are suppressed or killed off, the more resistant bacteria will increase (multiply) and fill the void. Always remember: nature hates a vacuum. Something will fill it.

All of this is concerning because many studies find that a greater variety of bacterial species is considered healthy and linked to lower levels of inflammation.

Disrupted microbial communities in those with sinusitis

This same process seems to be happening in the sinuses, with some species not just suppressed to low numbers, but permanently killed off by antibiotics. This can be seen in studies where the sinus microbiome of healthy people is compared to people with sinusitis. Keep in mind that an infection, allergies, toxins, other medicines – can also result in an imbalance in the sinus microbiome.

A groundbreaking study was published in 2012 finding that persons with chronic sinusitis (all of whom had taken courses of antibiotics) had a sinus microbiome that was depleted of many bacterial species when compared to healthy persons. One of the depleted species was the keystone bacterial species Lactobacillus sakei. A keystone species is one that has an important role in the health of the microbial community.

This depletion of many bacterial species was confirmed in numerous studies. One 2016 study by Santee et al compared bacterial communities between healthy children and those that had a history of acute sinusitis. They found a total of 951 species among the 47 children studied, with 308 species showing some "depletion" among children with a history of sinusitis.

Depleted bacterial species included those in the Akkermansia, Faecalibacterium prausnitzii, Clostridium, Lactobacillus, Prevotella, and Streptococcus groups.

Cochrane reviews (a highly regarded group reviewing studies) find that antibiotics don’t really treat acute sinusitis, and there also is “very little evidence that oral antibiotics are effective in patients with chronic rhinosinusitis”. So it appears that doctors are recognizing that antibiotics are ultimately not the answer for many sinus issues.

Probiotics for sinus infections

The future looks very bright regarding how to treat sinusitis. A number of researchers have suggested administering certain beneficial probiotic species (such as Lactobacillus sakei) locally in the nose or in the mouth to correct the microbial imbalance in the sinuses. This is because bacteria such as Lactobacillus sakei (found in Lanto Sinus) suppress and dominate over harmful bacteria.

This is why the use of probiotics to rebalance the sinus microbiome is so exciting. It’s a chance to really try to encourage beneficial microbes to flourish and repopulate in the sinuses.