Is it allergy season in Hawaii?

Hawaii's allergy profile is unlike any other US state. With no true winter, there is no annual pollen reset — grass species pollinate continuously year-round. The most significant wave is Japanese cedar (sugi), planted extensively in watershed forests on Oahu and other islands, which peaks from December through April. Non-native trees introduced over the past century — including macadamia, eucalyptus, and Queensland ash — add seasonal peaks. The windward coasts of each island receive more rain, which suppresses pollen; leeward sides are drier and can accumulate higher airborne counts. Mainland ragweed does not grow in Hawaii.

Hawaii's allergy geography is determined by the trade wind pattern. Windward coasts (northeast-facing) receive heavy rain that suppresses pollen. Leeward coasts are drier, warmer, and accumulate higher pollen loads. Oahu's Honolulu is leeward; Kaneohe is windward and significantly lower in pollen. The Big Island's wet Hilo side versus dry Kona side shows the same pattern dramatically.

Honolulu / Leeward Oahu

Drier, warmer — higher pollen accumulation

Honolulu sits on Oahu's leeward side where trade winds deposit pollen without the rain to wash it away. Japanese cedar from the Koolau uplands drifts downslope December through April. Bermuda and kikuyu grass pollinate continuously in the urban landscape. Skin-prick test panels on Oahu are heavily weighted toward Japanese cedar.

Japanese cedar · Dec–AprGrass year-roundMacadamia · Mar–May

Windward Oahu / Kaneohe

Heavy rain from trade winds suppresses pollen

Kaneohe and the Windward Coast receive some of the highest rainfall on Oahu. This significantly suppresses airborne pollen compared to Honolulu. Japanese cedar still peaks in winter but at lower levels. Grass pollen is present year-round but counts are generally lower than Honolulu.

Japanese cedar · Dec–Apr (lower)Rain suppresses countsGrass year-round (moderate)

Big Island / Hilo

Wet east vs. dry west — dramatically different profiles

Hilo on the Big Island's east side is one of the rainiest cities in the US — pollen is continuously washed from the air. The dry Kona side sees substantially higher counts. Macadamia nut farms are concentrated on the Big Island and produce significant pollen in spring. The volcanic landscape has limited introduced tree coverage compared to Oahu.

Macadamia · Mar–JunGrass year-roundHilo rain suppresses significantly

Maui / Valley Isle

Diverse microclimates — upcountry vs. lowland differences

Maui's central valley between Haleakala and the West Maui Mountains creates its own pollen corridor. Upcountry Maui (Kula, Makawao) grows produce agriculture that contributes grass and weed pollen. The resort areas of Wailea and Kaanapali are drier and see higher leeward pollen accumulation. Japanese cedar is present but less prominent than on Oahu.

Grass year-roundUpcountry agriculture adds weed pollenJapanese cedar · Dec–Mar

Each row shows a full year of pollen for one region — trees in blue, grasses in green, weeds in amber. Hawaii's grass row never fully drops to zero — look instead for months when tree pollen is lowest (June–October) for the best relative relief.

Oral Allergy Syndrome (also called pollen-food allergy syndrome) causes tingling or mild itching in the mouth when you eat certain raw foods during the relevant pollen season. The proteins in the food are similar enough to the pollen protein that your immune system cross-reacts. Cooking usually deactivates the offending protein, so the same food cooked may cause no reaction.

Japanese Cedar (Sugi) pollen

Tomatoes & citrus

Tomatoes, peaches, apples, kiwi, melon, beans (in some cases)

Peak risk December–April on Oahu and other islands with sugi plantings. Japanese cedar is the dominant winter-spring allergen in Hawaii and one of the most significant causes of allergic rhinitis statewide.

Bermuda & Kikuyu grass pollen

Tomatoes, potatoes & melons

Tomatoes, potatoes, kiwi, watermelon, cantaloupe, oranges (in some cases)

Year-round risk in Hawaii. Grass pollen never fully stops, which makes OAS management more complex than mainland states with defined seasons. Leeward locations have higher continuous exposure.

Guinea grass pollen

Wheat & melon cross-reactions

Watermelon, cantaloupe, kiwi, tomatoes, peaches (mild)

Peak risk May–August. Guinea grass is a tall non-native grass that grows prolifically in disturbed areas and roadsides across all Hawaiian islands. It produces substantial pollen through the warmer months.

Not medical advice. If you suspect OAS, speak with an allergist — it can sometimes progress, and symptoms that extend beyond the mouth should be evaluated.