I have allergies also so I take Zyrtec D. It does seem to help. It seems my allergies get worse from year to year.
It doesn't dry up mucous. Mucinex thins it out and helps you cough it up. Drink lots of water as well. You want to be able to cough it up and out. There are versions for sinus and chest, and time released. Use the one that makes sense to you. You can always get something else the next time.
I usually take one (400 mg.) in the morning and one at bedtime. Doctor said I could take up to 4 a day-depends on how bad a day you are having. Generic and brand names all have the same ingredient. I use the cheapest I can find. Hope this helps.
I take it twice a day... and lots of water