Background: Elaeis guineensis (oil palm) pollen is one of the most predominant species of inhalant allergens in the tropical Southeast Asia region; however, its association with the manifestation of allergic diseases remains largely unexplored. We aimed to determine the sensitization pattern of oil palm pollen and associate this with the risk and severity of allergic diseases. Methods: Participants were recruited as a part of the Singapore and Malaysia cross-sectional genetic and epidemiological study (SMCSGES). Two independent cohorts were recruited: n=564 serum samples were collected and serological assessment was performed against a panel of 16 crude inhalant allergens including house dust mite, pet, insect, pollen, and fungal allergens; n=13,652 Singapore/Malaysia Chinese young adults were recruited and skin prick test was used to assess oil palm sensitization, which was tested for its association with the risk and severity of asthma, allergic rhinitis (AR), and atopic dermatitis (AD). Results: The sensitization rate of oil palm pollen is 9.6% in the n=564 Singapore/Malaysia cohort. In the n=13,652 Singapore/Malaysia Chinese cohort, oil palm sensitization significantly associates with increased risks of asthma ( p=1.34x10 ^-4), AR ( p=2.91x10 ^-13), and AD ( p=6.95x10 ^-7). Asthmatic patients with oil palm sensitization have increased risks of wheezing ( p=0.00995), nocturnal cough ( p=0.0122), and exacerbations ( p=0.00139) in the past 12 months. AR patients with oil palm sensitization also have an increased risk of developing moderate-to-severe symptoms ( p=0.00113). Conclusions: We have identified significant associations of oil palm sensitization with increased risks, exacerbations, and the severity of symptoms of allergic diseases in the tropical Southeast Asian region (Singapore/Malaysia).