Microorganisms naturally present on or within your body, known as the human microbiota or normal flora, can cause illness. While typically harmless or beneficial, these resident “germs” can become pathogenic under certain conditions, highlighting the complex balance between our bodies and their microbial inhabitants.
Understanding Your Body’s Microbial Residents
The human body hosts trillions of microorganisms, including bacteria, viruses, and fungi, collectively known as the human microbiome. These residents are found on the skin, gut, respiratory tract, and other bodily surfaces. Most are commensals, living in a non-harmful relationship with their human host.
These microbial communities play many roles in maintaining health. Gut bacteria, for instance, break down complex carbohydrates, aiding nutrient absorption. They also synthesize vitamins like K and certain B vitamins. This ecosystem of “own germs” contributes to well-being.
When Commensals Turn Pathogenic
Beneficial microorganisms can become pathogenic and cause illness under specific circumstances. One mechanism involves opportunistic infections, where a weakened immune system allows normal flora to overgrow or spread to new, unprotected areas. For example, gut bacteria can cause serious infections if they enter the bloodstream.
Dysbiosis is another mechanism, an imbalance in the microbial community. Factors like antibiotic use, diet changes, or stress can disrupt the microbiome’s balance, leading to the proliferation of certain microbial species that cause disease.
Dormant viruses, known as latent viruses, can also reactivate and cause illness. Viruses like herpes simplex or varicella-zoster can reside in nerve cells for years without symptoms. Triggers such as stress, fever, or a compromised immune system can prompt these viruses to reactivate, leading to active infections.
Common Scenarios and Examples
Cold sores, caused by herpes simplex virus (HSV-1), are a common example. After initial infection, HSV-1 can lie dormant in nerve cells and reactivate periodically, triggered by stress or sunlight, leading to recurrent blisters. Shingles similarly results from varicella-zoster virus reactivation (the chickenpox virus). This virus can re-emerge decades later, causing a painful rash, typically in older adults or those with weakened immunity.
Gastrointestinal infections can arise from imbalanced gut bacteria. Clostridioides difficile (C. diff) infections often occur after antibiotic treatment, eliminating beneficial gut bacteria and allowing C. diff to overgrow and produce toxins. Yeast infections, particularly vaginal candidiasis, are caused by Candida albicans overgrowth, a fungus normally found on mucous membranes. Disruptions like antibiotic use, hormonal changes, or a weakened immune system can allow Candida to proliferate.
Skin infections can also stem from our own bacteria. Staphylococcus aureus, commonly found on skin and in the nose, can cause infections when entering a break in the skin, such as a cut. Urinary tract infections (UTIs) are frequently caused by Escherichia coli (E. coli), a gut bacterium. If E. coli migrates from the digestive to the urinary tract, it can cause infection.
Strategies for Prevention
Maintaining a robust immune system helps prevent illness from one’s own germs. This involves a healthy lifestyle, including a balanced diet and adequate sleep, which supports immune function. Managing stress through mindfulness or physical activity also helps, as chronic stress can weaken immune responses.
Practicing good hygiene prevents resident microbes from entering vulnerable areas. Regular handwashing reduces bacteria spread, and proper wound care prevents skin bacteria from causing localized infections. Using antibiotics judiciously, only when necessary and as prescribed, helps preserve the balance of natural microbial communities.
Managing underlying health conditions, especially those compromising the immune system, can reduce opportunistic infection risk. Vaccinations, like the shingles vaccine, can prevent latent virus reactivation by boosting the immune response. Some individuals also consider incorporating probiotics and prebiotics to maintain a healthy gut microbiome balance.