Which of the following is a common symptom of foodborne illness caused by bacteria?

Nausea and vomiting are common symptoms of foodborne illnesses caused by bacteria because these symptoms are part of the body's natural response to harmful pathogens. When bacteria or their toxins are ingested, they can irritate the gastrointestinal tract, leading to an inflammatory response. This often manifests as nausea and vomiting, which serve to expel the contaminated food from the body. Other symptoms may include diarrhea and abdominal cramping, but the presence of nausea and vomiting is particularly prevalent in cases of bacterial food poisoning.

Weight gain and high blood pressure are not directly linked to foodborne illnesses, as they represent chronic health issues rather than immediate reactions to food contamination. A skin rash, while it can be associated with some infections, is not a typical symptom of foodborne illnesses caused specifically by bacteria. Thus, the presence of nausea and vomiting is a clear indicator of such foodborne infections and signals that the body is reacting to an adverse health threat.