Ryegrass is often grown in lawns, but most of its pollen comes from pastures, wild areas and roadsides, since it usually has to be a foot tall to flower. Not to be confused with rye, a grain crop like wheat, ryegrass is one of the most potent and widespread of all grass allergens.
Habitat: Native to Europe, Asia and North Africa; cultivated worldwide
Description: Single-stemmed tuft grass
Allergenicity: Moderate to severe
Allergy season: June to August
Tips: If you have a ryegrass lawn, keep it mowed (or at least less than a foot tall). Beyond that, avoid unidentified grass pastures in summer, and consider staying indoors from 5 to 10 a.m. with the windows closed.