Data from more than 500,000 children in more than 50 countries suggests poor diet may be to blame for rising levels of these allergy-related conditions.
Those who ate fast food, such as take-away burgers, risked severe asthma, eczema and itchy, watery eyes.
Eating plenty of fruit appears to be protective, Thorax journal reports.
Fast food often contains high levels of saturated- and trans-fatty acids, which are known to affect immunity, while fruit is rich in antioxidants and other beneficial compounds, say the researchers.
In the study, children in their early teens who ate three or more weekly servings of fast food had a 39% increased risk of severe asthma. Continue reading Fast-food linked to childhood asthma and eczema