Rosacea is a chronic condition that is characterized by facial redness, flushing, dilated blood vessels on the face, small red bumps, pus-filled bumps, and sometimes skin thickening (mostly of the nose).
The cause of rosacea is not known but as more research is conducted, it is becoming clear that it has to do with abnormal function of the immune system. In this process, the cells of the immune system react and overreact to various elements in the skin that normally they tolerate. Although the immune system in rosacea is not functioning properly, there does not appear to be an infection causing the disease (by bacteria, fungus or a virus for example). This may sound strange to people with rosacea because the most commonly prescribed medications for rosacea are all in the antibiotics family – which are medications that were originally used to treat infection.
This begs the question: if rosacea is NOT an infection, why do doctors prescribe antibiotics to treat it?
Medications are often used for more than one medical problem. When we ingest a pill or introduce any drug into our bloodstream, the entire body is exposed to the effects of the drug. In turn, every system in the body (such as the skin, the immune system, the gastrointestinal system, the lymphatic system, the nervous system and so on) will react differently to the medication. This is the reason why every medication has side effects. In fact, it is very rare to have a medication (or any treatment for that matter) act as a silver bullet and affect one system alone. An important goal in developing drugs is to decrease unwanted side effects, but adverse effects happen all the time. In the process of studying a drug, adverse effects are recorded and any unexpected positive effects are noted too. One recent example is the observation that people treated with the medication bimatoprost for glaucoma developed longer eyelashes leading to its use in people with shorter eyelashes or patients after chemotherapy who were trying to grow hair back.
The case of antibiotics is no different. Many classes of antibiotics have an unexpected but desirable anti-inflammatory effect on the human immune system, in addition to their expected ability to kill bacteria. In the case of rosacea, this has been especially true for the tetracycline family of antibiotics, which were originally developed to treat bacterial infections. It is also true for medications such as metronidazole and ivermectin which were originally developed to treat parasite infections. Doxycycline is the only tetracycline medication that is specifically FDA approved for treatment of rosacea in the United States, but other tetracyclines like minocycline are often used “off label.” Research studies demonstrate that doxycycline has specific anti-inflammatory activities that may help to treat rosacea.
Doxycycline’s properties include:[5,6]
- Inhibiting certain types of white immune cells (lymphocytes and neutrophils)
- Decreasing amounts of reactive oxygen species and increasing scavenging of those damaging molecules
- Reduction in the enzymes known as matrix metalloproteinases that normally breaks down skin collagen
Doxycycline has better results in the treatment of papulopustular and ocular types of rosacea that are classically associated with higher levels of inflammation.
One might ask: who cares? Just take the antibiotic medication and move on. However, the problem with this approach is the potential development of antibiotic resistance by bacteria. When millions of prescriptions are written to attack trillions of bacteria, it is practically inevitable that at least one of those bacteria will evolve to become immune to the killing effects of the antibacterial drug. More commonly, killing the bacteria that are sensitive to the drug leaves their resistant “cousins” alive. With less competition, these dangerous bacteria can grow and begin infecting humans. This may not be a big deal in the case of rosacea, however, if a patient in the hospital has a serious lung infection with bacteria that are resistant to antibiotics, that is a big deal. Simply put, careless use of antibiotics may lead to the development of dangerous resistant bacteria. That is why there is a recent call for all prescribers to use extra caution when prescribing antibiotics. If you ever went to the doctor with a viral illness and the doctor refused to write an antibiotic, that is probably the reason!
How can doctors reconcile this problem? Antibiotics work for rosacea but can increase bacterial resistance. Using antibiotics at lower doses may be the solution. Using a lower dose still maintains the anti-inflammatory effects of the medications. The lower dose seems to be safe and does not induce significant bacterial resistance. Common sense dictates that using lower doses can also reduce the frequency of side effects of the medication. Finally, there is an effort to shorten the overall length of time that patients take the medication so that patients are not overexposed to antibiotics. By using low doses of doxycycline, doctors are able to give anti-inflammatory doses for the treatment of rosacea without creating doxycycline resistant bacteria.