If it is medicine, take it as scheduled, just make sure not to overdose. If you miss the period then just wait for the corresponding one, don't take a double dose at one go. Most important of all, you'll probably want to seriously make an effort to rest if the doctor recommends it. Try to reallocate your other work and study commitments as best as you can. The better you feel the faster you recover. When in doubt about anything, consult your doctor.
however, this won't work for everyone, so seek a doctor if the following doesn't help;
Things to do
1) Remove yourself from wherever you believe the allergens are coming from. Sometimes it might not be an allergy, but a flu, in those cases, you would also want to see a doctor. Sometimes stress can also exacerbate the situations, take things in work-life balance more easily for this period of time. Some over the counter drugs might also work if you remember your doctor's previous prescriptions. Sometimes it doesn't hurt to check the internet out for new cures and different methods.
2) Usual Symptoms of sinus allergy involves copious amounts of nasal fluids, or a runny nose.
To relief your sinus, its best if you have a running nose, to just blow it all out as often as you can. You can either use a pack of disposable tissues, or go to the nearest toilet and remove the entirety of the gunk there. It is best not to use a handkerchief, or the fluids will just stick to your handkerchief, which you would then have to spend time washing, not to mention, that would also be unhygienic.
3) if you find yourself having phlegm due to the infection or allergy in your throat, something sicky and uncomfortable at the back of your throat would be a working description, then you need to get it out of your body fast! It's full of yucky germs and pus and dead cells or allergens that are detrimental to your body. Usually your body will naturally cough it out, if it doesn't you can stimulate a cough by exhaling sharply and hardly. It is best to cough into a sink or at the very least a tissue. Often you'll taste something slightly salty,that's a good sign in that your body is doing it's job kicking out the things making you sick. Occasionally there might be some remnants at the back of your mouth, use your tongue to scoop them up and spit them out. If you have running nose, occasionally the goo will sneak into your throat, just do the same as the above.
4) Finally, if the doctor is one you trust, try to follow the doctor's advice!