PracticalDermatology

Oral antibiotics have held a vital role in the treatment of common skin conditions ever since they were introduced into mainstream healthcare during the 1930s.¹ Aside from the clear impact these drugs have on harmful bacteria, oral antibiotics serve a useful anti-inflammatory function, making them a valuable tool in dermatologists’ efforts to combat inflammatory conditions such as acne and rosacea.² Oral antibiotics are also frequently prescribed before and following operations to reduce the chance of surgical complications, although it is worth noting that such practices have significantly decreased in recent years.

That said, the sheer ubiquity of these applications is striking. In 2017, dermatologists in the United States generated an incredible 6.1 million outpatient antibiotic prescriptions.³ One recent CDC report found that dermatologists prescribe more oral antibiotics courses per clinician than any other specialty, with many of those prescribed courses extending for several months at a time.⁴

The consequences of over-prescribing—and the need to curtail antibiotic prescriptions—have been well-established, and dermatologists’ use of antibiotics has seen a modest decline over the last several years as a result.^2,3 Antimicrobial resistance currently stands as the third leading cause of death in the United States; as many as 162,044 people die each year from medication-resistant infections. The problem has spurred action; today, many health systems now emphasize the importance of limiting antibiotic prescriptions.

This shift away from antibiotic use across medicine has been driven primarily by concerns over antimicrobial resistance; however, dermatologists have also begun to consider the ways that antibiotics can negatively impact the microbiome and, by extension, general health and skin health.

Up until recently, conversation on the matter has centered on the gut microbiome in particular, with relatively little focus on the cutaneous microbiome. Research into the microbiome’s impact on human health only began a decade or so ago, and our understanding of the topic is understandably limited. That said, it seems likely that dermatologists’ increased understanding of how the microbiome influences skin health can help improve care for patients in the future. However, investigation into the matter is still in its early stages and those in the sector will need to remain informed of research conclusions as they develop.

the Microbiome and Its Link to Dermatology

Much of the research we do have available has focused on the gut microbiome, rather than the cutaneous. What we do know is that gut microbiota plays a crucial role in metabolic and immune functions; it prevents the proliferation of potentially pathogenic resident species and limits the damage caused by infectious agents. The gut microbiome also contributes to the development of the immune system and assists in the body’s fight against major conditions and—most importantly for dermatologists—inflammation.^5,6

Comparatively less is known about the cutaneous microbiome; however, some research does indicate a similarly robust link between the skin microbiota and dermal health. One paper published in a 2019 issue of the Journal of Dermatology noted that patients with severe acne tend to harbor significantly altered microbiome diversity when compared to those with lesser or no acne.⁷

Because these and other early investigations suggest that the microbiome serves as a crucial component of the epidermal barrier, supporting the cutaneous microbiome could help patients improve and maintain their skin health.⁷

Antibiotics Negatively Impact the Microbiome—And Potentially Skin Health

At the same time, research suggests that the drugs that limit microbiota—i.e., antibiotics—might also have an inadvertently negative impact on dermal health.⁵ One 2010 study published in PLOS ONE that looked into the effect that clarithromycin and metronidazole—drugs commonly used to address H. pylori, a bacterium that can cause stomach ulcers and cancer—had on the gut and throat microbiomes found a dramatic reduction in bacterial diversity across all subjects treated with antibiotics. Though the microbiota diversity eventually recovered to its pre-treatment levels, researchers noted that levels could remain in disarray for up to four years after a course of antibiotics.⁸

The longstanding disturbance is notable—and troubling—because a lack of diversity can have a considerable negative impact on microbial activity and microbiome function, particularly in children. A growing body of research suggests that childhood exposure to antibiotics increases the risk for conditions including but not limited to diabetes, celiac disease, allergies, asthma, and inflammatory bowel disease.^9,10

Moreover, other studies have indicated that antibiotic-caused changes to the microbiota are not limited to the gut, but also occur in the oral, respiratory tract, and vaginal microbiomes.⁵ Though research has not explicitly determined oral antibiotics’ impact on the cutaneous microbiome, it seems reasonable to consider that oral antibiotics may also disrupt the skin’s microbiota. That said, the effect of antibiotics on specific microbiomes has not been extensively researched. More investigation will be needed to understand how oral antibiotics may impact the cutaneous microbiome and dermal health.

With that said, the information dermatologists do have at hand prompts the questions: What can we do to support patients’ microbiome and, in a longer view, leverage our improved understanding of the gut and cutaneous microbiota to effectively support patients’ microbiomes and treat skin disease?

Microbiome Care And Dermatology Treatments

Some evidence suggests that the use of pre- and probiotics might help improve skin health over time. Modulation of the gut microbiome has been found to aid the treatment of skin diseases and even induce remission in patients with rosacea. Topical medications can also be useful; one study published in a 2019 issue of Microorganisms reported that patients with mild to moderate acne who applied topical treatments of a bacteriocin experienced a significant reduction in inflammatory lesions compared to those who used a placebo.¹¹

Interestingly, some topical skincare products may already, unintentionally, support cutaneous microbiome health. Topical formulations that use prebiotics and other longstanding skincare ingredients such as niacinamide and shea butter have been found to help improve microbiota diversity and potentially benefit skincare health. Moisturizers, in particular, are notably useful in bolstering the cutaneous microbiome.¹² Moreover, some of these products may even offer long-term aid. One recent study published in the Journal of Drugs in Dermatology found that some applied compounds can remain on the skin for weeks after first use.¹³

Low-dose versions of antibiotics, such as doxycycline, may also be useful in microbiome-considerate treatments. These drugs, typically prescribed at 40mg or less, are too weak to have any antibiotic properties but strong enough to have useful anti-inflammatory effects. A review published in Clinical, Cosmetic and Investigational Dermatology established the efficacy and safety of low-dose antibiotics in treating rosacea without adverse effects on antimicrobial resistance in 2009.¹⁴ It may be worth considering such a low-dose solution for those who need antibiotics long-term, given that it may help patients without harming their microbiome or worsening antibiotic resistance.

Given all of this, it’s unsurprising that cosmetic and medical companies have begun to express interest in incorporating pre- and probiotic ingredients into their products. But their forays must be viewed with caution. Currently, dermatologists only have limited research or evidence to apply to their practice. However, it stands to reason that dermatologists should continue moving away from antibiotic-reliant strategies and towards a more holistic approach that uses both topical treatments and lifestyle changes to support patients’ lifelong dermal health.

Before that transition can happen, however, dermatologists need access to more information. It’s true that research efforts are underway and that dermatologists should be applying new findings to their practice. But our current understanding is limited; we need more research on the cutaneous microbiome and how it influences skincare health. Future efforts should also consider how antibiotics impact skin microbiota, if there are consequences specific to the skin that short- and long-term use of antibiotics might cause, and which treatments are most effective in helping patients achieve a healthy microbiota diversity.

The conversation around the role that antibiotics and the microbiome play in maintaining lifelong health is ongoing—and for dermatologists, it has barely begun. One point is clear: for both our patients’ sake and our own understanding of skin health, we need to develop a better understanding of how microbiomes stand to influence skin conditions—and the way we treat them.

1. Carrasco DA, Vander Straten M, Tyring SK. A review of antibiotics in dermatology. J Cutan Med Surg. 2002 Mar-Apr;6(2):128-50.

2. Barbieri JS, Bhate K, Hartnett KP, Fleming-Dutra KE, Margolis DJ. Trends in Oral Antibiotic Prescription in Dermatology, 2008 to 2016. JAMA Dermatol. 2019 Mar 1;155(3):290-297..

3. New Effort Seeks to Address Antibiotic Resistance Via Legislation. Practical Dermatology. https://practicaldermatology.com/articles/2019-oct/new-effort-seeks-to-address-antibiotic-resistance-via-legislation?c4src=issue:feed.

4. Center for Disease Control (2013). Outpatient Antibiotic Prescriptions -- United States. CDC.gov. 2013.www.cdc.gov/antibiotic-use/community/pdfs/Annual-ReportSummary_2013.pdf.

5. Ferrer M, Méndez-García C, Rojo D, Barbas C, Moya A. Antibiotic use and microbiome function. Biochem Pharmacol. 2017 Jun 15;134:114-126.

6. Stiemsma LT, Michels KB. The Role of the Microbiome in the Developmental Origins of Health and Disease. Pediatrics. 2018 Apr;141(4).

7. Li CX, You ZX, Lin YX, Liu HY, Su J. Skin microbiome differences relate to the grade of acne vulgaris. J Dermatol. 2019 Sep;46(9):787-790.

8. Jakobsson HE, Jernberg C, Andersson AF, Sjölund-Karlsson M, Jansson JK, Engstrand L. Short-term antibiotic treatment has differing long-term impacts on the human throat and gut microbiome. PLoS One. 2010 Mar 24;5(3):e9836.

9. Arrieta M-C, Stiemsma LT, Dimitriu PA, Thorson L, Russell S, Yurist-Doutsch S, et al. Early infancy microbial and metabolic alterations affect risk of childhood asthma [Internet]. Science Translational Medicine. American Association for the Advancement of Science; 2015. Available from: https://stm.sciencemag.org/content/7/307/307ra152?ijkey=7c7d70d76ee6f300476bc0dbe2a8d05458266cf4&keytype2=tf_ipsecsha

10. Blaser MJ. Antibiotic use and its consequences for the normal microbiome [Internet]. Science. American Association for the Advancement of Science; 2016 [cited 2020Feb11]. Available from: https://science.sciencemag.org/content/352/6285/544

11. Catinean A, Neag MA, Mitre AO, Bocsan CI, Buzoianu AD. Microbiota and Immune-Mediated Skin Diseases-An Overview. Microorganisms. 2019 Aug 21;7(9).

12. Strugar TL, Kuo A, Seité S, Lin M, Lio P. Connecting the Dots: From Skin Barrier Dysfunction to Allergic Sensitization, and the Role of Moisturizers in Repairing the Skin Barrier. J Drugs Dermatol. 2019 Jun 1;18(6):581.

13. Yu Y, Dunaway S, Champer J, Kim J, Alikhan A. Changing our microbiome: probiotics in dermatology. Br J Dermatol. 2020 Jan;182(1):39-46.

14. Valentín S, Morales A, Sánchez JL, Rivera A. Safety and efficacy of doxycycline in the treatment of rosacea. Clin Cosmet Investig Dermatol. 2009 Aug 12;2:129-40.