A. Fever by itself is not harmful or dangerous and is unlikely to cause brain damage or other problems. Also remember that a child's temperature can vary during the day, and can normally reach a high point of 100.2 degrees F at about 6pm.
Fever is not a disease, instead, it is a symptom that can accompany many childhood illnesses, especially infections. In general, you should call your pediatrician if your infant under three months of age has a rectal temperature above 100.4 degrees F, if your infant aged 3-6 months has a temperature above 101 degrees F, or if an infant above 6 months has a temperature above 103 degrees F.
For most older children, it is not so much the number, but rather how your child is acting that is concerning. If your older child is alert, active and playful, is not having difficulty breathing, and is eating and sleeping well, or if the temperature comes down quickly with home treatments (and he is feeling well), then you don't necessarily need to call your doctor immediately.
However, it is important to keep in mind that a fever is not the only sign of a serious illness. While some children are fine with a temperature of 104 degrees, others can be deathly ill with a temperature of 101 degrees or even without a fever or a low temperature.
Whether or not your child has a fever, if he is very irritable, confused, lethargic (doesn't easily wake up), has difficulty breathing, has a rapid and weak pulse, is refusing to eat or drink, is still ill-appearing even after the fever is brought down, has a severe headache or other specific complaint (burning with urination, if he is limping, etc), or if he has a fever and it is persistent for more than 24 to 48 hours, then you should call your pediatrician or seek medical attention immediately.
Also, you should call your doctor if your child has a fever and another medical condition (heart disease, cancer, sickle cell, immune system problems, etc.). When in doubt, call your doctor when your child has a fever, especially if you think that your child is ill appearing.
Treatment of a fever can include using an over-the-counter fever reducer, including products that contain acetaminophen (Tylenol) or ibuprofen (Motrin or Advil). If you child has an infection, using a fever reducer will not help your child to get better any faster, but they will probably make him feel better.
You should also give your child a lot of fluids when he has a fever, so that he does not get dehydrated. Keep in mind that treatment of a fever is usually to help your child feel better, so if he has a fever, but doesn't feel bad, especially if the fever is low grade, then you do not need to treat the fever.