Spring brings beautiful flowers and fragrant lilacs, but also heavy tree pollen that coats cars and triggers sneezing, wheezing, and headaches. As an allergist and immunologist at the University of Colorado School of Medicine, I frequently help patients with seasonal allergies, and the recurring question is whether each season will be worse than the last. With a record warm start to spring 2026 across much of the United States, the answer is a teary-eyed yes.
What Are Allergies?
More than one in four U.S. adults suffer from seasonal allergies, a number expected to rise as climate change prolongs and intensifies pollen seasons. Allergies refer to allergic rhinitis or allergic conjunctivitis—inflammation of the nose or eyes due to allergen exposure. Symptoms include itchy, watery eyes, runny nose, sneezing, congestion, and nasal itching, typically appearing in spring, summer, and fall when allergens are airborne.
The primary driver of seasonal allergies is a protein in pollen, the male reproductive material released by plants. When the immune system develops an allergic antibody called IgE to these proteins, and multiple IgE molecules bind to the allergen upon contact with eye or nasal tissues, cells release histamine, prostaglandins, and leukotrienes. These molecules interact with blood vessels and nerves, triggering the familiar symptoms.
Which Pollens Cause Symptoms?
Pollen season begins with trees in late winter and early spring across many U.S. regions. However, not all trees follow this schedule; for example, mountain cedars (juniper trees) release yellow pollen from November through January in Texas, causing cedar fever. As spring progresses, grasses emerge, with their pollen causing symptoms from April to July. Later, ragweed and other weeds release pollen that triggers symptoms until a freeze halts production in autumn.
What Makes a Season Worse?
Several factors influence seasonal allergy severity, primarily the length of the growing season and pollen abundance—both increasing. Over recent decades, rising global temperatures have lengthened growing seasons across North America. Trees begin emerging from dormancy once temperatures exceed about 40 degrees Fahrenheit (4 degrees Celsius). In 2026, an unprecedented warm spring drove early tree pollen emergence in the Western U.S. In some locations, the growing season is now two weeks longer on average than in the 1990s and over four weeks longer than in the 1970s.
Another key factor is rising atmospheric carbon dioxide from fossil fuel combustion, which boosts plant growth, leading to longer pollination periods and more pollen production. Higher pollen counts cause more people to develop symptoms, and I have seen increasing numbers of patients experiencing allergies for the first time. Windy days can also disperse pollen widely, while rain temporarily scrubs it from the air. However, humidity and moisture after rain can rupture pollen granules, making them easier to inhale—especially grass pollen.
How to Avoid Symptoms
Managing allergy symptoms involves several strategies. First, reduce allergen exposure at home by keeping windows closed during pollen season, wiping pets with a damp towel to remove allergens, and avoiding clotheslines to keep washed items pollen-free. Changing clothes or showering after being outdoors also helps. Using HEPA air purification (non-ionizing, as ionizing filters generate ozone) can lower household allergen levels.
Monitor pollen forecasts from the National Allergy Bureau to anticipate high counts, which are generally highest in the morning. However, outdoor air pollutants like particulate matter (PM2.5) and ozone peak in midday and afternoon heat.
Do Medications Work?
Medications can alleviate symptoms. Saline nasal rinses reduce mucus and allergens in nasal passages. For mild symptoms, daily nonsedating (second-generation) antihistamines are effective. For moderate to severe allergies, daily nasal steroids can help, though they may take weeks to reach peak effect. Nasal antihistamine sprays offer additional benefits, and antihistamine eye drops can relieve eye symptoms. In dry climates like Colorado, nasal hydration with saline sprays eases congestion.
If medications are insufficient, consult an allergist about immunotherapy (allergy shots), which involve weekly and monthly injections over several years. While effective at reducing symptoms and medication needs, they carry side effects like local reactions, asthma symptoms, and rare risk of anaphylaxis.
Allergies can be miserable but manageable—even in an overproductive year like 2026. Understanding causes and finding the right solutions can help you enjoy flowers and sunny walks.
