Expert Health Articles

Seasonal Allergies: A Month-by-Month Guide

Amber Patterson, MD

ENT & Allergy Specialists of Northwest Ohio

Seasonal allergies often get lumped into one category. However, each season has its own unique allergens. Follow the guide below to see which months you can expect to see a flare up of which allergens.

Spring: February - May

For spring allergy sufferers, the joys of warmer weather, birds chirping and flowers blooming come at a price. Bothersome nose and eye symptoms, breathing difficulties and skin allergies can set in as trees begin to pollinate. Tree pollen season occurs between February and May in Ohio. Season length and timing varies each year depending on weather. In 2019 for example, due to a long, harsh winter, trees did not begin pollinating until March. Because pollen is microscopic, we cannot see it in the air and often do not know when the season has started until symptoms begin.

A common myth regarding spring allergies is that because symptoms often start in correlation with blooming flowers, the flower pollens contribute to the problem. Our allergies are due to plants that spread pollen by wind (anemophilous plants), which is how the pollen enters our eyes, noses, mouths or skin. These plants are not showy or eye-catching because they do not need to be. The plants we typically notice are usually flowering plants that are pretty for the purpose of catching the attention of pollinators like bees and other insects. These plant pollens are spread from plant to plant by the insects that visit them (entomophilous plants). For this reason, most of our pollen exposure is due to pollen in the air outdoors, and thus our allergies are to wind-pollinated plants.

Many trees are primarily pollinated by wind, and tree pollens are the main springtime allergen. Mold spores also contribute to spring allergies but are most bothersome in the fall. Common trees in the northwest Ohio region that contribute to allergy symptoms include oak, cottonwood, birch, maple, sycamore, ash, elm, hickory, walnut, beech and mulberry. There is limited cross-reactivity between tree pollens. This means that while some trees are related and pollens are somewhat similar, many tree pollens have unique features that prevent the ability to create a single treatment for tree pollen allergy. Allergists are specially trained physicians who can test patients to multiple different tree pollens and treat each patient uniquely for their specific tree pollen allergies.


Summer: May - June

Late spring and early summer allergies mainly involve grass pollen. In the allergy world, we often think of Memorial Day as a reminder of peak grass pollen season. Northern pasture grasses like June/Kentucky Blue, Timothy, Orchard and Rye are commonly grown in the Midwest. They begin pollinating in May, peak toward the end of the month and carry through the first few weeks of June.


July Hiatus

Even allergies take a vacation. Hot, dry July weather tends to give a short reprieve for pan-pollen allergic patients (those allergic to tree, grass and weed pollens). Trees and grasses are no longer pollinating. Without rain, mold spore counts are often low and fall plants have not yet begun the pollination process.


Fall: August - November

Back-to-school time often marks the onset of weed pollination and resurgence of allergy symptoms. The term “hay fever” is often used to describe these symptoms and is derived from the “illness” that farmers used to obtain when harvesting hay in the fall. With the discovery of pollen allergies, it was recognized that fall symptoms were due to ragweed pollen rather than due to hay exposure. August 15 is endearingly referred to amongst allergists as the start of ragweed season. Other common weed plants that produce pollen allergens include English plantain, lamb’s quarter, pigweed, Russian thistle, yellow dock, sorrel, firebush, cocklebur and marsh elder.

Mold spore counts tend to rise dramatically in the fall with falling leaves and dying plants. Molds thrive in the decomposing plant matter and their spores float into the air. Gardening in mulch or dirt, farming or hiking in the woods can also increase exposures to mold spores this time of year.


Winter: December - January

While this article primarily focuses on pollen season, the only “seasonal” allergen we encounter during winter in the Midwest is mold. Mold grows best above freezing temperatures and when it is damp, such as after rainfall. During warm periods of winter, mold spore counts can temporarily spike, which can be confusing for mold allergic patients that may not be expecting an allergy flare during winter months.


For seasonal allergy sufferers, it is important to meet with a board-certified allergist to identify which allergens are most bothersome and to allow for more focused attention on avoidance measures and treatment options.