Yes, your own feces can make you sick, though this generally requires specific circumstances. Feces is biological waste containing a massive population of microorganisms, including bacteria and viruses, typically confined to the digestive tract. While these microbes are usually harmless or even beneficial inside the gut, their presence outside the body creates a potential risk for re-ingestion and subsequent illness. Understanding the composition of this waste and the mechanism of contamination is the first step in mitigating this risk.
What Feces Contains
Feces is complex, consisting of about 75 percent water and 25 percent solid matter. The solid portion is primarily composed of undigested food matter, dead cells shed from the intestinal lining, and a vast microbial population. Up to 55 percent of the solid matter in feces consists of bacterial biomass, representing the body’s normal gut microbiota.
A single gram of feces can contain hundreds of billions of bacteria, along with millions of viruses. These microbes, which include strains of E. coli and Bacteroides, are considered “normal flora” and are either helpful or benign when confined to the colon. However, if these organisms are ingested, they can become opportunistic pathogens capable of causing infection. The brown color and distinct odor of feces are byproducts of bacterial action on waste materials.
The Mechanism of Self-Infection
The primary pathway for self-infection is known as the fecal-oral route of transmission. This mechanism describes how pathogens exit the body in the stool and then enter the mouth of the same person. This transfer is typically indirect, involving contaminated hands, objects, or surfaces that are subsequently brought into contact with the mouth.
When a person fails to properly wash their hands after using the toilet, microscopic amounts of fecal matter containing these microbes can remain. These contaminated hands can then touch door handles, food, or the face, completing the cycle of self-contamination and ingestion. This route allows bacteria, viruses, and parasites that thrive in the gastrointestinal tract to establish a new infection.
Increased Risk Factors for Self-Contamination
The risk of self-contamination increases significantly under specific circumstances that introduce more harmful pathogens into the feces or compromise the body’s defenses. Being actively ill with a gastrointestinal infection raises the risk, as the stool contains high concentrations of pathogenic organisms like Norovirus, Salmonella, or C. difficile. These infectious agents are often capable of causing illness even in small doses, making contamination a greater threat.
Individuals with compromised immune systems, such as those undergoing chemotherapy or with certain chronic conditions, face a higher risk because their bodies cannot effectively fight off opportunistic infections. Fecal incontinence, which can be caused by long-term diseases like inflammatory bowel disease, also presents a higher risk of environmental contamination. Activities that involve close contact with feces, such as changing diapers, require extra vigilance, as accidental exposure increases the potential for transmission.
Essential Hygiene Practices
Preventing self-infection relies on interrupting the fecal-oral cycle through consistent and diligent hygiene practices. The single most effective action is proper handwashing using soap and clean, running water. Hands should be scrubbed for a minimum of 20 seconds, ensuring that all areas, including under the fingernails and between the fingers, are thoroughly cleaned.
This practice should be strictly followed after using the toilet, before preparing or eating food, and after handling waste such as diapers. Beyond personal hygiene, routinely cleaning and disinfecting high-touch surfaces in the bathroom, such as toilet handles and sink faucets, helps to eliminate environmental contamination. By adhering to these simple steps, the risk of transferring microbes from waste back into the body is substantially minimized.