Welcome to the
Allergy Hub

Tree pollen is a fine, powdery substance released by trees as part of their reproductive process. Pollen can be large or too small to be seen. When tree pollen travels through the air or is carried by the wind, it can settle on the eyes, nose, or mouth and trigger allergy symptoms. In the U.S., tree pollen is often the leading cause of allergies in February and April. However, in some southern states in the U.S. such as Florida, Georgia, and Alabama, some trees may produce pollen as early as December or January. Common tree pollen that triggers allergies includes oak, birch, cedar, elm, pine, pecan, sycamore, and hickory. Check your local pollen forecast for your area’s timing.

Grass pollen is a fine, microscopic particle released by grass that can trigger an allergy when inhaled or when in contact with the skin. Grass pollen is the most common cause of allergies during late spring through summer, roughly May through July, and longer in warm southern climates. Grass season runs longer in warm climates, so check your local pollen forecast for what’s active near you. Some common grass species that can trigger allergies include: Bermuda grass, Johnson grass, Kentucky Bluegrass, Orchard grass, sweet vernal grass, and Timothy grass.

Weed pollen is the most common cause of allergies in late summer and fall (August to November). However, in warmer climates, weeds can release pollen year-round. Weed timing varies by region and can run year-round in warmer areas, so check your local pollen forecast for your area. Some common weed species that can trigger allergies include: Ragweed, curly dock, pigweed, sagebrush, and Russian thistle.

Molds are tiny fungi that thrive in warm, damp environments and reproduce by creating spores that float in the air, just like pollen. Molds can be found indoors and outdoors. In the United States, mold spore counts are often highest in July (in warmer states) and October (in colder states). On the West Coast and in the South, mold spores can be year-round.

Pet dander is tiny flakes of skin cells that are shed by animals with fur or feathers, such as cats, dogs, rabbits, guinea pigs, and birds. In addition to dander, some people may be allergic to proteins found in their pets' saliva, urine, and feces.

Other allergens that can trigger allergies include house dust mites, cockroaches, certain insects, and occupational allergens (e.g., flour, wood dust, or natural rubber latex gloves).