You may have already noticed the trend in rising allergies among your friends. Or your children and their friends. And at first, you might have thought it was your imagination. But the truth is that allergies of all kinds are on the rise. And scientists know little more than you do.

We’ve already discussed how childhood hygiene may play a role in rising allergies. Shockingly, a 2008 CDC report shows that in the past decade, the rate of food allergies in children has risen by 18%! And hospitalizations of children due to food allergies have nearly quadrupled. These rates are similar to those in other countries across the world.

By some estimates, 8% of children have food allergies, along with 4% of adults. And a new study has scary numbers for those children; nearly 70% of young children with allergies suffer a life-threatening attack, and in 70% of those cases, caregivers failed to provide the correct epinephrine treatment.

For parents of children with food allergies, every day can be trying and terrifying. Most severe reactions occur by accident. An innocent treat given to a child by a friend’s parent or a teacher. Snack foods with long ingredient lists that get misread. Or even safe foods that become contaminated when prepared or served alongside foods containing allergens.

When a child is diagnosed, parents may find themselves searching for clues as to what may have caused the allergy. Our previous article covered two common theories: the Hygiene Hypothesis and the Old Friends Hypothesis.

But what really causes food allergies in children?

One of the biggest predictors of food allergies is family history. If your relatives have allergies, or even conditions such as asthma and eczema, you may be more likely to have food allergies. This genetic factor also means that if you have one type of allergy (say hay fever), it is highly likely that you will have another type of allergy as well. Many allergy sufferers also have asthma, which can increase the likelihood of severe food allergies.

Environment also plays a large, although more mysterious role. A study from just last year shows that kids who grow up in crowded cities seem more likely to suffer food allergies than children in rural areas. This supports years of research with similar findings.

Curiously, some children outgrow their allergies around age four or five—around 1 in 4 children can eventually eat foods that would have once caused severe reactions. But researchers have noted that as the rate of allergies in the population increase, the average age at which children outgrow allergies has also increased.

Unfortunately, beyond these few connections, scientists still don’t understand why people may gain or outgrow allergies.

But luckily, there are several treatments like immunotherapy that can help children tolerate foods they once couldn’t. By exposing children to very small amounts of the allergen, allergists can monitor their response and eventually expose them to higher and higher amounts. It may not completely cure the allergy, but it can at least make accidental ingestion safer, and ease parents’ minds.

Read more about one mom’s search for the cause of her son’s allergies. And find out how respiratory and seasonal allergies can be connected to food allergies.