Hi, thank you for posting your query on health care magic.
If you are suffering from Nasal polyp,then it should be seen on an MRI.
However,CT scan is a more better option than an MRI if you are suffering from Nasal Polyps.
And yes,allergy can be a cause of your condition.
You may find relief by taking the following medications:
Antiallergic like Levocetrizine with
montelukast,
Steroid nasal drops like
Mometasone,
Decongestant nasal drops like
Oxymetazoline in case of nasal blockage:Dont use them more than 7-10 days,
Analgesic like Ibuprofen in case of Headache.
It would be advisable to have an Allergic testing done to find out which substances you are allergic to ,so that you can take precautions to avoid those substances.
It would also be advisable to consult an
ENT specialist doctor,for the Endoscopic examination of your nose.
Hope this answers your question.Take care.