Taking Tylenol or aspirin when you have the flu is okay as long as you're 18 or older.
If you are under the age of 18 then you should not take any Tylenol or aspirin with the flu because it can lead to a rare condition known as Reye's Syndrome.
Reye's Syndrome although rare is a serious condition that causes swelling in the brain and liver and can lead to death and it happens from those under 18 recovering from the flu or viral infection especially when they are taking pain medicines such as Tylenol or Aspirin.
But as long as you're 18 or older then taking Tylenol or Aspirin should be perfectly fine and safe.
I take Tylenol when I have the flu virus to help with the fever, headaches, muscle aches etc.