Which of the following is not a common symptom of a foodborne illness?

Elevated blood pressure is not typically associated with foodborne illnesses. Foodborne illnesses usually present symptoms that directly relate to gastrointestinal distress, such as nausea, diarrhea, and sometimes fever. These symptoms arise from the body's response to pathogens, toxins, or irritants present in contaminated food.

Nausea and diarrhea are common symptoms as they indicate the body's effort to expel harmful substances. Fever can occur as part of the immune response to infection. However, elevated blood pressure is not a standard symptom linked to foodborne illnesses, making it the correct choice in this context.