Common symptoms associated with fever include sweating, shivering, headaches, muscle aches, poor appetite, rash, restlessness and general body weakness. High fever can lead to symptoms of mental dysfunction, such as confusion, excessive sleepiness, irritability and convulsions (seizures).
Convulsions triggered by fever (febrile seizures) are common among children younger than 5 years. These seizures usually occur at the beginning of an illness when temperature rises rapidly. In infants and toddlers, febrile seizures typically cause muscle rigidity and generalized convulsions that last less than 15 minutes. A febrile seizure usually is followed by a long period of sleep.
Specific symptoms associated with a fever often can provide clues to help identify the fever's cause. For example, a fever accompanied by vomiting and diarrhea may signal gastroenteritis, and a fever associated with coughing, shortness of breath and grayish-yellow phlegm may indicate pneumonia.