My 3.5 year old daughter had 104 fever. she didn't complain about other symptoms. fever went away with tylenol came back at 3am but she woke up with no fever. @4pm she had 101 iwhen measured in her buttocks and 98!under her armpit, any thoughts what's

Probably viral bug: Many viral infections will have fevers that spike and resolve as you are describing. These changes can be with and without such things as tylenol (acetaminophen) and ibuprofen. Other common symptoms of the "viral prodrome" can be achiness/muscle pain, headache, and sometimes nausea. In general, if your child has no significant symptoms, just watch and hydrate.Don't be surprised if a rash appears in the next day!

Best temp is rectal: The most accurate temp is rectal especially for kids under two. We consider a temp above 100.5 and advise to give tyleno for temps over 101 and adivil .Etc above 102.5. A child with any fever that is not acting well should seek medical attention asap. I would generally call the doctor for a temp above 103 if the fever doesn't respond to meds or the child doesn't look well. When in doubt call.