Nasal infections like sinusitis and frequent colds rise during monsoon due to increase in humidity, which creates a breeding ground for microbes, Dr Darshil Vaishnav said. Allergens like mold spores and dust mites also trigger nasal issues, he added. Bacteria and viruses can cause natural openings of the sinuses to swell and block, leading to sinusitis, Dr Sanjay Sachdeva stated.