Why Do Antibiotics Help With Inflammation?

Inflammation is one of your body’s primary defenses against trauma or foreign invasion. Swelling, redness and other signs of inflammation represent part of an automatic reaction to a wide variety of insults, ranging from a minor scratch to a life-threatening infection. This is especially true with bacterial infections, when your immune system switches on to help keep the infection localized, kill invading microorganisms and set the stage for healing and recovery. But inflammation also causes pain and discomfort and can lead to other health problems in cases of allergy and autoimmune disorders. Antibiotics help your immune system overcome an infection by killing or limiting the growth of bacteria, and accumulating evidence suggests that some antibiotics might also play a role in limiting the inflammatory response itself.

An inflammatory response is automatically triggered whenever your body detects a threat, whether from a wound, sports injury or a foreign invader like bacteria. The response begins almost instantly, with increased blood flow to the area and changes in the blood vessel walls that allow more fluid and inflammatory white cells to pass from the circulation into the damaged tissue. As white cells move into the area and become activated, they release chemicals and enzymes that help kill bacteria, summon more white cells and further fuel the inflammatory response. These blood flow changes and cellular reactions lead to the redness, swelling, increased warmth and pain associated with an area of inflammation. These processes also lay the groundwork for tissue healing once the injury or infection resolves. Unfortunately, the same inflammatory response can lead to ongoing pain and disability when associated with allergies, autoimmune disorders or other chronic diseases.

The term “antibiotic” commonly refers to a drug with antibacterial activity. Although certain medications are available to treat fungal, parasitic and viral infections, the vast majority of antimicrobial drugs work only against bacteria. These antibiotics can be divided into several large classes, based on their chemical structures or method of action. For instance, antibiotics can be classified as either bactericidal, meaning they kill bacteria, or bacteriostatic, meaning they block bacterial multiplication without direct killing. Your immune system is capable of fighting off many infections without the use of antibiotics, but it does so more quickly and easily when antibiotics help block bacterial growth. More serious or deep tissue infections, such as meningitis and pneumonia, require antibiotics to prevent life-threatening complications.

The recommended uses for antibiotics are limited almost exclusively to cases of known or suspected bacterial infection, which are always associated with inflammation unless the immune system is severely weakened. The dose and length of antibiotic treatment depends on many factors, including the type of infection; the specific bacteria identified and its susceptibility to different antibiotics; the patient's age, body size and kidney function; the presence of other medical conditions, such as pregnancy or breastfeeding; and the antibiotic’s biochemical and metabolic properties. An effective antibiotic treatment plan combined with a normal immune response results in the destruction of the infecting bacteria, which, in turn, removes the stimulus for inflammation. As healing begins, the blood vessels shrink, white cells stop moving into the area, chemical signals driving the inflammation are shut off and healthy new tissue starts to grow.

Antibiotics decrease inflammation in the vast majority of cases because clearing an infection removes the reason for the inflammation. However, a number of studies since the 1990s have contributed to the idea that some antibiotics might also directly limit or change the inflammatory response, as discussed in the December 2007 issue of “Rhinology.” Several classes of antibiotics, including the macrolides, tetracyclines and the beta-lactams, when used in certain chronic illnesses, appear to decrease inflammation in addition to their antibacterial effects. This research represents a mix of experimental and clinical studies, some performed only on cell cultures rather than patients. The antibiotics mentioned show a variety of ways they might affect the inflammatory response, including changing inflammatory cell metabolism, altering cytokines and other chemicals that stimulate and help maintain inflammation, and speeding the breakdown and removal of inflammatory cells. Any or all of these mechanisms could act to decrease inflammation.

Antibiotics can help cure infections more rapidly, save lives and might play a role in the future in modifying or limiting the complications of chronic inflammation with disorders such as chronic airway disease, rheumatologic disorders, multiple sclerosis or even strokes. The positive effects of antibiotics, however, must be balanced with their potential problems, including side effects, drug interactions, changes in normal bacterial populations in the body and increases in bacterial resistance to antibiotics. These risks will have to be kept in mind when considering the use of antibiotics for purposes other than fighting bacterial infections, especially when other, more specific anti-inflammatory drugs are available.