Hi.. Thanks for the query.. Allergic reaction can cause blockage of the sinuses that can be due to fluid accumulation causing congestion.. You can first of all try to un-block your sinuses by using decongestant nasal spray like Xylometazoline or Oxymetazoline. You can also do steam inhalation so that the mucous becomes loose and drains off.. Do saline nasal irrigation and use a humidifier in your room.. In case if you still do not find any relief you can consult an Emergency room and get evaluated so that they can do a sinus x ray. You can be advised antibiotics if there are signs of sinus infection along with oral decongestants like Phenylephrine, anti allergics like Levocetrizine and other remedies as I advised before.. Hope this helps.. Regards..