Purpose: The purpose of this study was to analyze the effects of a health education program to improve knowledge about environmental health and allergy symptoms among elementary school students. Methods: This study has nonequivalent control group pre-post test design. Participants of this study were 60 elementary students (30 experimental and 30 control) who agreed to participate in the study. The education program consisted of information on environmental health and allergies, the atmosphere, indoor environments, food and allergies, and activities with parents. The program was carried out one time (50 minutes) per week during 6 weeks. Knowledge and symptoms of allergies were recorded before and after the program among both groups. The collected data were analyzed by ANCOVA and t-test using SAS program. Results: There was a significant increase in knowledge about allergies in the experimental group compared to the control group, but allergic symptoms were similar in the two groups. Conclusion: These findings suggest that environmental health education programs are effective in the area of school health nursing for increasing knowledge about environmental health and allergies. Further research is needed to develop programs for reducing allergic symptoms as an environment health problem among children.