Pollen allergies, also known as hay fever or allergic rhinitis, occur when the immune system overreacts to pollen from trees, grasses, and weeds. Symptoms can include sneezing, runny or stuffy nose, itchy eyes, and fatigue. These reactions happen when pollen enters the body and triggers the release of histamines, leading to inflammation. Pollen levels vary throughout the year, with peak seasons typically in spring for tree pollen, late spring to summer for grass pollen, and late summer to fall for weed pollen. People with pollen allergies can manage symptoms through medications, avoiding outdoor activities during high pollen counts, and using air purifiers indoors.