When allergy reactions and sinus congestion cause pain and fever, Acetaminophen relieves these symptoms. Assuming a contact dermatitis allergy rather than an anaphylactic reaction. A typical dose of acetaminophen (Tylenol, APAP) can treat muscle aches and pain, fever. Children under the age of 12 should not take salicylates (aspirin) due to the potential for Reye syndrome. Normal dosing won't affect the immune system, so it won't directly affect an allergic reaction.