Which of the following symptoms is specifically associated with gastrointestinal upset?

The selection of nausea, vomiting, or diarrhea as the answer is accurate because these symptoms are hallmark indicators of gastrointestinal upset. Gastrointestinal upset commonly involves disturbances in the digestive system, which can manifest through these specific symptoms.

Nausea refers to the sensation of an urge to vomit, while vomiting is the act of expelling the contents of the stomach. Diarrhea involves the frequent passage of loose or watery stools, which is often a response to irritation or infection within the gastrointestinal tract. Collectively, these symptoms directly reflect issues within the digestive system and are recognized as primary indicators of gastrointestinal disturbances, such as food poisoning, infections, or other digestive disorders.

In contrast, skin irritation can arise from numerous causes but does not directly indicate gastrointestinal issues; instead, it is more related to dermatological concerns. Headache and fatigue, while potentially linked to a range of health problems, also do not specifically indicate gastrointestinal upset and are instead more general and can be caused by various factors, including stress or dehydration. Fever reduction is not a symptom at all but rather a treatment goal when fever is present, unrelated to specific gastrointestinal discomfort. Therefore, the symptoms in the selected answer are the most directly associated with gastrointestinal upset.