Hay fever is also known as pollinosis or seasonal allergic rhinitis. For most people, a single allergen sets their symptoms off at about the same time each year. Spring attacks are usually due to tree pollen (not hay), while grass pollens dominate in the summer and weed pollens in the autumn.
Hay fever is an atopic or allergic disease like asthma. This means the body tends to overreact to certain types of outside particles. One way it overreacts is by releasing histamine, a chemical present in many important animal cells. Histamine is a major cause of the symptoms of hay fever including sneezing, runny nose, and even coughing. Hay fever, like asthma, can be inherited.
People inherit the general tendency to be allergic but not always specific allergies. For example, if a mother has hay fever to ragweed, her child is at an increased risk of hay fever, but the child may be allergic to other allergens. Children have a 30% chance of developing hay fever if one of their parents is affected and a 50% chance if both have hay fever.
These are some of the pollens most likely to cause an allergic reaction:
- spring: tree pollens such as oak, elm, maple, alder, birch, juniper, and olive
- summer: grass pollens such as Bermuda, timothy, sweet vernal, orchard, and Johnson; and weed pollens like Russian thistle and English plantain
- fall: weed pollens, especially ragweed