What is a characteristic of a moderate contrast reaction?

A moderate contrast reaction typically presents with symptoms that are more pronounced than those of a mild reaction but are still not life-threatening. Extensive urticaria, or hives, is a common and well-documented characteristic of moderate reactions to contrast agents. Such reactions may involve widespread skin involvement, leading to significant discomfort for the patient but generally don't involve severe complications.

The correct choice reflects the understanding that moderate reactions can escalate in intensity and may lead to various systemic symptoms, among which extensive urticaria is highly representative. In contrast, symptoms such as minimal nausea, metallic taste in the mouth, or flushing of the skin might be seen but are generally more aligned with mild reactions or are not exclusively characteristic of moderate reactions.