The number of children and teenagers affected by asthma and eczema has been increasing, and the big question has been why. Now it appears that our consumption of fast food may be one of the reasons. New research has found a link between eating fast food and kids’ likelihood of developing eczema, an autoimmune skin condition, and Asthma.

The study was massive — it followed 319,000 children aged 13-14 in 51 different countries, and 181,000 children aged 6-7 in 31 different countries, all of whom were part of the International Study of Asthma and Allergies in Childhood (ISAAC). Participants and their parents answered questions about whether they (or their kids) suffered from asthma, allergies, or eczema, over the last twelve months. They also answered questions about the kinds of foods they tended to eat most often or most infrequently, including fish, fruits, vegetables, cereals, pasta, bread, rice, meat, butter, margarine, eggs, milk, and, of course, fast food and burgers.

Fruits and vegetables seemed to offer a protective effect. Eating these foods at least three times per week was associated with a 14% reduction in symptoms severity in younger kids, and an 11% reduction in teens.

Fast food was the only type of food to be linked to symptoms of the three conditions studied in teenagers – and it was linked to severe symptoms of all three, regardless of socioeconomic status or gender. In the young children, the relationships were less straightforward, but still considerable. In general, the authors found a 39% increased risk for symptoms of any of the three conditions in teens, and a 27% increased risk in younger children.

The risk for the conditions was lower in those kids and teens who ate more fruits and vegetables. They seemed to offer a protective effect. Eating these foods at least three times per week was associated with a 14% reduction in symptoms severity in younger kids, and an 11% reduction in teens.

As always in this kind of study, the results do not imply that fast foods causation – for example, that fast food causes eczema, asthma, or hay fever – only that there is a correlation between the variables. There could be other factors at play, not taken into account here, which could influence risk of any or all of the three conditions.

Still, the authors say that it’s certainly possible that causality is involved, and this could have big implications. "If the associations between fast foods and the symptom prevalence of asthma, [hay fever] and eczema is causal," they write, "then the findings have major public health significance owing to the rising consumption of fast foods globally." Though we may not understand all the connections at this time, there is no downside to eating less fast food and more fruits and vegetables. So skip the fast food joint, especially if you have kids, and make a quick, healthy meal at home instead. And make sure to pay attention to the types of meals you order when eating out.

The study was carried out by a team at the University of Auckland, and published in the British Medical Journal, (BMJ).