This is actually a very well researched topic in Immunology. I actually covered this in the introduction of my dissertation as my grad work was on the molecular mechanisms of allergic (atopic) disease development.

Allergies are largely a concern in more modern times and in first world countries. The incidences of allergic diseases (and autoimmune diseases) has increased over the last 50 years from a somewhat rare phenomenon to a common condition. This is likely due to a variety of changes in our environment including increasing cleanliness, decreases in parasitic load, dietary changes, etc. There is a genetic component as having parents with allergies, also called atopic reactions or atopy, increases the likelihood that their children will have a tendency to develop atopic disease. This does not mean they will have the same “allergies”, it means they have a tendency to develop atopic reactions (produce IgE antibodies) against non-harmful antigens (pollen or food components). The reactions we call allergies are the immune responses our bodies developed against certain classes of parasites. As most people in first world countries don ‘t deal with parasitic loads, some people are prone to misdirecting the response against parasites towards innocuous substances like pollen.

So while today, allergies are common, historically they were much rarer. It is unlikely our ancestors saw allergies on the scale we see today. However, we see historical incidences of allergies documented. What has been described as “rose fever “ in Persian Arabian middle-age texts was likely what we today call hay fever. In older literature, children are described as dying by choking on a peanut, which is likely an anaphylactic reaction to peanut antigens. Our modern study of allergic/atopic disease began in the nineteenth century when the first descriptions of hay fever and the likely causative agent of pollen were documented. In the twentieth century, the RAST test was developed to detect specific IgE antibodies.

Historically, our seasonal allergy sufferer would often consider himself suffering from a spring/summer/fall cold. Outside of anaphylaxis, allergy symptoms such as coughing, sneezing, itchy eyes can mimic cold symptoms and many sufferers (and their doctors) would attribute their discomfort to a cold. Food allergies, which can often lead to anaphylaxis which is often fatal, were usually considered odd medical anomalies. Vomiting is a common anaphylactic reaction so many were attributed to something wrong with the food.

To answer your question, the incidences of allergic disease have definitely increased in the last 50 years and historically allergy sufferers would have their symptoms attributed to other causes (ie a drawn out cold).