An adviser with Allergy New Zealand says the pollen season has started earlier than normal because of a mild winter and signs of an early spring.
The agency, which provides information and advice, believes about one in five New Zealanders suffer from allergies associated with pollen.
Adviser Penny Jorgensen says pollen from pine trees, grass and weeds can affect human health more than other types of pollen.
She says that's because the pollen dust is lighter than the sort found in trees and travels more easily in the wind.
Ms Jorgenson says pollen can affect sleep, as people allergic to it can't breathe through the nose. It can also trigger asthma.
She says the season usually finishes in March.