A dangerous temperature for adults is a temperature over 103 degrees Fahrenheit, while dangerous temperatures in children are higher than 104 degrees and infants require medical attention for temperatures exceeding 100.4 degrees, according to Mayo Clinic and WebMD. Temperatures can be taken under the arm or in the mouth. Rectal temperatures are most accurate in infants.
Any temperature over 100.4 in an infant under the age of four months should be treated promptly as it can be life-threatening. A normal body temperature is 98.6 degrees Fahrenheit, though some people's natural temperatures may vary slightly. A fever can be caused my many things, including viruses and infections. Some of the symptoms that can accompany a fever include fatigue, rash, sore throat, vomiting and fussiness.