Which of the following is an emergency requiring a visit to the ER or hospital?

A temperature of 95 degrees Fahrenheit or lower, when measured rectally, indicates hypothermia, which is a medical emergency. Normal body temperature typically ranges from approximately 97 to 100.4 degrees Fahrenheit. A reading significantly below this range can lead to serious health risks and complications requiring immediate medical attention.

In contrast, a headache is common and may not necessarily indicate a serious condition; slight bruising is often minor and can happen due to a variety of benign reasons; and seasonal allergies, while they can cause discomfort, typically can be managed with over-the-counter medications and do not require emergency intervention. Thus, among the options listed, the low temperature is the one that signifies a condition requiring urgent care.