Do weather changes cause or exacerbate allergy symptoms?

Weather Changes and Allergy Symptoms

Weather changes do not directly cause allergies, but they significantly influence allergen exposure patterns and can trigger or exacerbate symptoms in sensitized individuals through changes in pollen counts, mold spore concentrations, and allergen distribution. 1

Understanding the Mechanism

Allergic rhinitis is caused by an IgE-mediated inflammatory response to inhaled allergens—not by weather itself. 1 However, weather patterns fundamentally control when and how much allergen exposure occurs:

How Weather Affects Allergen Exposure

• Seasonal pollen patterns are entirely dependent on geographic location and climatic conditions, with tree pollen predominating in early-to-mid spring, grasses in late spring/early summer, and weeds from late summer until early fall in temperate regions. 1

• Pollen counts correlate directly with daily symptom scores and medication use during allergy seasons. 1

• Specific weather conditions dramatically alter allergen concentrations: sunny, windy days with low humidity produce higher pollen counts, while gentle sustained rain temporarily reduces airborne pollen. 1

• Temperature and humidity changes affect fungal spore release, with some fungi requiring moist conditions (elevated during rain and dew formation at night), while others release spores in dry, windy conditions. 1

The Priming Phenomenon

• Nasal sensitivity to seasonal allergens increases as the pollen season progresses due to the "priming" effect—repeated allergen exposure enhances inflammatory responses. 1, 2

• Symptoms may decline more slowly than pollen counts at season's end because of this cumulative inflammatory priming. 1

Climate Change Impact

Climate change is extending pollen seasons and increasing allergen exposure year-round, fundamentally altering the traditional "seasonal" versus "perennial" classification:

• Elevated temperatures and increased carbon dioxide levels produce prolonged and more robust pollen seasons for most plant taxa studied. 3, 4, 5

• In tropical locations with year-round pollen seasons, distinguishing seasonal from perennial allergic rhinitis becomes clinically impossible based on history alone. 1

• Air pollution from climate change works synergistically with allergens to enhance immunogenicity and worsen asthma in susceptible individuals. 4

Extreme Weather Events

• Typhoons and heavy rain can paradoxically increase allergic rhinitis and atopic dermatitis by concentrating airborne allergens (pollen, ozone, fungus) on the sixth to seventh lag day after the event. 6

• High temperature periods worsen existing allergic symptoms in 22.4% of those with skin allergies and 15.7% with nasal allergies, compared to normal days. 7

Clinical Classification Framework

The American Academy of Otolaryngology-Head and Neck Surgery recommends classifying allergic rhinitis by three parameters rather than relying solely on seasonal patterns: 1

1. Pattern of allergen exposure: seasonal (pollen), perennial (dust mites, mold, animal dander), or episodic (intermittent environmental exposures)
2. Frequency of symptoms: intermittent (<4 days/week or <4 weeks/year) versus persistent (>4 days/week and >4 weeks/year)
3. Severity: mild (not interfering with quality of life) versus moderate-to-severe (causing sleep disturbance, impairment of daily activities, or work/school problems)

Common Pitfalls

• Do not tell patients that "weather causes their allergies"—this creates confusion about the underlying IgE-mediated disease mechanism. 1

• Avoid assuming seasonal patterns are predictable—many patients have perennial allergic rhinitis exacerbated by seasonal pollen exposure, and polysensitization is common. 1

• Recognize that patients may need year-round treatment rather than seasonal therapy, especially given climate change effects on pollen seasons. 3, 5

• The dose of allergen needed to trigger symptoms depends on individual sensitization levels and existing nasal inflammation, not just absolute pollen counts. 1