Seasonal Allergies (Hay Fever)

What happens in the body to cause allergy symptoms?

Allergies are an overreaction by the immune system to an otherwise usually harmless substance, causing the release of IgE antibodies. Upon repeat exposure, these antibodies act on mast cells, sparking the release of histamine and other inflammatory mediators.

Histamine is primarily responsible for the immediate itching and sneezing, whereas other molecules are tied to congestion, increased secretions, and other symptoms. Most allergies develop during early childhood, though some can also begin later in life.

Why do some people have seasonal allergies and others don’t?

Seasonal allergies have a strong genetic component, but their severity depends on a complicated set of environmental triggers that include initial intensity or dose of the allergen, age and immune status at time of exposure, and frequency of exposure.

Some other emerging risks that contribute to the rising worldwide prevalence of seasonal allergies include increased air pollution, decreased time spent outdoors in childhood, changes in the way buildings are ventilated, diets low in fresh food, and more caesarean section births. Reduced exposure to environmental microbes is another area that is receiving attention.

Are there other allergies or conditions that can make seasonal allergies worse?

Seasonal allergies can be more disruptive if someone has anatomic factors—like nasal polyps or a severely deviated septum—that predispose them to nasal congestion. Perennial allergies, like dust mite or animal dander allergies, can also amplify the immune response.

Can seasonal allergies increase the risk of other health problems? What are the implications of not managing them?

Children with allergic rhinitis are more predisposed to middle ear infections. Likewise, adults with allergies have an increased risk for sinus infections, likely due to stasis and poor clearance of mucus. And swollen upper airway tissue has implications for other breathing problems--like snoring, which can impair sleep.

More vague symptoms include fatigue, irritability, productivity loss, and impaired learning and decision making. Surprisingly, there is a higher rate of migraines in people with allergies, though there isn’t a clear causative role here.

Are there any associated patterns for people to look for with other sensitivities?

Atopy is the word we use to describe an allergic response in the body, and people with seasonal allergies have a higher incidence of other atopic conditions than the general population. Asthma, eczema (atopic dermatitis), and pollen-food allergy syndrome are some examples of atopic conditions.