Which of the following is a potential side effect of antibiotics?

Gastrointestinal disturbances are a well-known potential side effect of antibiotics. These medications can disrupt the normal balance of gut bacteria, leading to symptoms such as diarrhea, nausea, bloating, and abdominal pain. This occurs because antibiotics are designed to kill bacteria, and while they target harmful pathogens, they can also affect beneficial bacteria that are vital for digestive health.

The other options provided do not accurately represent typical side effects of antibiotics. Increased energy levels and improved immune function might be perceived as benefits, but they are not recognized side effects related to the pharmacological action of antibiotics. Skin hydration typically is unrelated to antibiotic use and is more associated with topical treatments or other systemic medications. Thus, gastrointestinal disturbances clearly align with the common risks associated with antibiotic therapy, making it the correct response in this context.