All sorts of allergies tend to run in families. However the allergy may not be in the same form. A parent with eczema or asthma may have a child who suffers from hay fever and vice versa. Modern research has been able to show that some members of a family may have an underlying tendency to allergy but are symptom free whereas other members have hay fever, asthma or eczema. The reasons for this are not entirely understood but it seems that exposure to any allergy producing substances , such as pollen , in infancy may increase the risk of developing an allergy in later life.
Hay fever is a modern disease.
It was virtually unknown before 1800 and has become common only during the last hundred years. The first case to be described medically was in 1819 but the causes of the disease were not identified until 1873. Medical statistics show that the incidence of hay fever rose steadily during the nineteenth century in many countries including France, Germany and the United States. The numbers of people affected by hay fever have continued to increase since 1900 and it has become prevalent in countries, such as Japan ,where it was unknown 40 years ago. It has been suggested that the statistics do not show a real increase but just record the fact that nowadays people recognise hay fever and to do something about it .