It is unusual to develop a yeast infection from an antihistamine alone, but if using Azelastine combined with Fluticasone (a corticosteroid), a yeast infection is more likely. Azelastine-Fluticasone can suppress the immune system generally and within the nasal passages. This can allow fungal organisms such as candida to thrive where they would normally be kept in check.
Symptoms of a fungal yeast infection can be identical to chronic or acute sinusitis, including congestion, pain, and fever. You may also develop more severe complications such as erosion or ulcers in the nasal passages, headaches, and confusion. If you suspect you may have a fungal sinus infection, you should seek in-person treatment at the earliest possible time.