Which statement accurately describes a side effect of antibiotics?

Antibiotics can disrupt the balance of normal flora in the gastrointestinal tract, which often leads to diarrhea as a common side effect. This occurs because antibiotics kill not only the harmful bacteria causing an infection but can also diminish the helpful bacteria that assist in digestion and maintaining gut health. As a result, the disruption may lead to gastrointestinal symptoms such as diarrhea.

In contrast, the other statements are not accurate reflections of antibiotic side effects. While some individuals may experience allergic reactions, it is not a universal effect and does not occur with every antibiotic. Additionally, antibiotics do not improve digestion; rather, their primary purpose is to eliminate bacterial infections. Finally, stating that antibiotics have no side effects is misleading, as they do indeed carry various potential side effects beyond diarrhea, including allergic reactions, nausea, and more.