Japanese cedar “sugi” (Cryptomeria japonica) is one of the major causes of seasonal allergies. Its pollen is one of the most potent known and may cause severe symptoms; stuffy and/or runny nose, itchy eyes, and sneezing. In Tokyo, one out of four people are believed to suffer from this allergy. The pollens are typically present from the end of January until May. Residents of Tokyo who have been exposed are at higher risk of developing seasonal allergies.