My son's pediatrician told us that fever lower than 107 is generally harmless for adults. However, children under 1 year should be seen by a doctor whenever they have a temp no matter how low it is.
Well, not quite. Children are far more resilient and capable of tolerating higher temps that would be dangerous for an adult. The problem is that the area of the brain responsible for temperature regulation isn't as well developed in small children as it is in adults. So that if a child's temp continues to increase, they may need intervention to keep the temp from reaching dangerous levels whereas an adult can be left to his own auto-regulatory devices, usually.
A temperature of 104 is HIGH for an adult. Children can hit 104 from the slightest illness or infection. If my mother had a dollar for every time I had a temperature of 104 as a child...wait...maybe that's why I have these unexplained seizures?
j/k
That's not to say that you shouldn't be concerned about a 104 degree temp in a child, because you cannot know whether it will go higher nor how quickly it may increase.
Edit: The last time I had a temp of 104 as an adult they wanted to keep me for observation. You bring a small child into the ER with a temp of 104 and its 'ho-hum come back if it goes higher'.