What causes seasonal allergies?

Quick Scoop: Seasonal allergies are usually caused by your immune system reacting to airborne particles that appear at certain times of year, especially pollen and mold spores. Common triggers include tree pollen in spring, grass pollen in late spring and summer, ragweed in late summer and fall, and mold spores during warm, humid seasons.

[1][3][9]

Main causes

  • Tree pollen often triggers symptoms in early spring.
    • [3][7][1]
  • Grass pollen is common in late spring and summer.
    • [7][1][3]
  • Ragweed pollen is a major fall trigger.
    • [1][3][7]
  • Mold spores can worsen symptoms in spring, summer, and fall, especially in damp or humid conditions.
    • [9][3][1]

Why symptoms happen

Seasonal allergies happen when the immune system treats harmless airborne substances like pollen as a threat, which leads to sneezing, a runny nose, itchy eyes, and other allergy symptoms. Different regions can have different allergy seasons, so the timing can vary depending on where you live.

[3][9][1]

What can make them worse

  • Warm, windy, or dry weather that spreads pollen.
    • [3]
  • High humidity that supports mold growth.
    • [1][3]
  • Changing climate conditions that can lengthen pollen seasons and increase pollen potency.
    • [1]

If you want, I can also give you a simple chart of spring vs. summer vs. fall allergy triggers or tips for reducing exposure.