Alder

Alder is an early-season pollinator closely related to birch. In the Pacific Northwest, alder is the dominant allergenic tree. Red alder (Alnus rubra) is the most common species in western North America. Alder pollen contains allergens that cross-react significantly with birch.

If you're allergic to alder pollen, you may also react to:

• Birch (strong cross-reactivity)
• Hazel
• Hornbeam
• Same fruit cross-reactions as birch (apples, pears)

• In the Pacific Northwest, alder is often the first tree to trigger allergies, starting as early as January.
• Alder cross-reacts with birch — if you're allergic to one, you're likely allergic to both.
• The same fruit cross-reactions apply: raw apples, pears, and stone fruits may cause oral tingling.