Dear hereorthere,
When you were a child, it was not so easy to diagnose peanut or other food allergies. Children with such allergies or deficiencies (such as celiac) were labeled as sickly, or failing to thrive.
Through Hashem’s mercy, doctors are today able to pinpoint the problem to specific allergy. This is clearly mercy, rather than punishment, because there is much less illness, death and pain as a result of this knowledge.
There are many diseases that may appear to be proliferating when in fact it is better diagnosis that makes them appear more common.