As allergy season is about to kick into high gear, I thought it might be interesting to review how another country like Japan tackles ocular allergies. Like North America, there has been an exponential rise in sensitization by 2.6-fold from 1980 to 2000 due to the prevalence of Japanese cedar pollen (JCP, sugi-pollinosis).1
During the height of allergy season between February and April, a large number of patients with sugi-pollinosis experience more severe symptoms for longer periods of time compared to other pollen allergies. In this case, aerobiology might hold the explanation because JCP is dispersed in large quantities over long distances (>62 miles in some cases) and can remain airborne for more than 12 hours.2
Previously from Dr. Cooper: Substance P: Dry eye and allergy’s mixed signal or missing link?
Japanese cypress pollen is dispersed in April and May immediately after the release of JCP, causing a “sandwiching” effect of pollen exposure. This cross reactivity has allowed an elongation of the allergy season in many parts of Japan with annual climate variations leading to healthcare problems that affect daily activity, work productivity, learning, sleep, and quality of life (QOL) in people of all ages.3
What’s in a number?
In 1993, the Allergy Integrated Project Epidemiologic Investigation Group of the Ministry of Health and Welfare surveyed the entire Japanese population. Researchers found the proportion of people with bilateral ocular itching at 16.1 percent in children under age 15 and 21.1 percent in adults.4
The proportion of people with allergic conjunctival diseases diagnosed by ophthalmologists was 12.2 percent in children and 14.8 percent in adults.4 From these results, the proportion of people with allergic conjunctival diseases in the entire Japanese population is estimated to be 15 to 20 percent. If this statistic sounds familiar, you would be right because the U.S. figure is the same on a macroscale.5,6
A research group on allergic ocular disease of the Japan Ophthalmologists Association conducted epidemiologic surveys of all patients with allergic conjunctival diseases who were treated across Japan in 28 different facilities from January 1, 1993, to December 31, 1995. Researchers found female patients with seasonal and perennial allergic conjunctivitis (SAC or PAC) outnumbered male patients 2-to-1, whereas male patients with vernal keratoconjunctivitis (VKC) outnumbered female patients 2-to-1.7