Allergen: A substance that can cause an allergic reaction. Common allergens include ragweed pollen, animal dander, and mold. SLIDESHOW Could I Be Allergic? Discover Your Allergy Triggers See Slideshow From Allergies Resources Seasonal Impact of RSVLearn How to Treat Chronic HivesBreaking Out in Hives When You're Nervous? Featured Centers What Are the Best PsA Treatments for You?Understanding Biologics 10 Things People With Depression Wish You Knew Health Solutions From Our Sponsors Shot-Free MS Treatment Your Child and COVID-19
