I hated when they pulled all the OTC drugs for little kids, Pediacare really worked well for us. My 3 yr old boy weighs the same as my 6 yr old girl and I can't give him meds but I can give her meds...HUH?
Benadryl in an Antihistamine. It's job is to dry up snot and stop mast cells from going off in an allergic reaction.
Sudafed causes the blood vessels in the sinus area to react and cause sinus pressure to change so snot/nasal congestion can be released.
Most OTC chest congestion drugs are Guaifenesin. Some, like Delsyn, do have other medication but almost all have this expectorant in them. They cause the mucus int he throat and lungs to stay runnier so they can be coughed up.
Sometimes doctors will recommend using a nebulizer and Xophenex (best choice for kids) or Albuterol to help kids have a more productive cough. It dialates the bronchial tubes therefore the mucus is easier to get out, plus the nebulizer vials have some steril water in the mix and that helps loosen the goo too.
My pediatrician told me there is no research that show the "DM" part of cough syrups works.
Fever usually means the body is fighting off infection somewhere. It's over 100 degrees, time to go to the doctor.
Use humidifiers all the time, warm showers several times a day, take all the meds the doctor gives, drink clear liquids like water, beware of fluids disguised as hydrating drinks, they can be mostly flavored salt water, salt water drys you out.