Sinusitis can be triggered by anything that inflames or irritates the nasal cavity or sinuses, from smoke to pollen to fungus. In many cases, sinusitis is triggered by substances similar to allergens, although this is not always the case. For example, pollen, a common allergic trigger, may irritate the sinuses leading to sinusitis, but acute sinusitis may also be caused by the common cold, which is separate from allergies.