A fever is technically any body temperature above 98.6, but most doctors are not concerned until the fever gets above 100.4. Make no mistake, fevers are never associated with allergies. If you have a fever, that means your body is trying to fight off an infection. It might be hard to tell what symptoms are your illness and which are allergies, but talking to your doctor about a fever coupled with a sore throat or a runny nose will help them to diagnose you sooner. It’s important that you get the right treatment. An antihistamine won’t help fight the flu, and antibiotics won’t help your allergies.