Firstborn children may be more likely to suffer from certain types of allergies, a new study finds.

Japanese researchers surveyed parents of more than 13,000 children aged 7 to 15 and found a child's birth order did not seem to affect the prevalence of asthma or eczema.

However, firstborn children were more likely to have hay fever, pink eye due to allergy and food allergy. In fact, the investigators found the prevalence of food allergy was 4 percent in firstborn children, 3.5 percent in second-born children and 2.6 percent for children born later.

"It has been established that individuals with increased birth order have a smaller risk of allergy. However, the significance of the effect may differ by allergic diseases," first author of the study, Dr. Takashi Kusunoki, of the pediatrics department at Shiga Medical Center for Children and Kyoto University, both in Japan, explained in a news release from the American Academy of Allergy, Asthma & Immunology.

Further research is needed to learn more about how birth order affects allergy risk, Kusunoki and colleagues concluded.