What is pollen?

Each grain of pollen is tiny (microscopic). When there is a lot of pollen together it becomes a fine yellow powder. It's made of the male reproductive cells of flowering plants, trees, grasses, and weeds. It's the most common cause of hay fever (seasonal allergic rhinitis).

Which plants make pollen that causes allergic reactions?

Plants that spread their pollen by the wind are the most common cause of allergic rhinitis. They include:

• Trees. These include oak, Western red cedar, elm, birch, ash, hickory, poplar, sycamore, maple, cypress, walnut, catalpa, olive, and pecan.

• Grasses. These include timothy, Johnson, Bermuda, orchard, sweet vernal, rye grass, and some bluegrasses.

• Weeds. These include ragweed, sagebrush, redroot, pigweed, Russian thistle (tumbleweed), lamb's quarters, and English plantain.

The pollen of most flowering plants, such as roses, is heavy, waxy, and spread by insects. These plants generally don't trigger allergies.

When is pollen season?

Each type of plant has a pollen season. Some plants bloom in the spring, and others bloom in the fall. Pollen season often starts in the spring. But it may begin as early as January in the western U.S. The season often lasts until November.

Can allergic rhinitis in pollen season be prevented?

To reduce the effects of allergic rhinitis during pollen season, do the following:

• Keep windows closed during pollen season. Use air conditioning with a HEPA filter if possible. This cleans, cools, and dries the air.

• Reduce outdoor activities early in the morning between 5 a.m. and 10 a.m. This is when pollen is most common.

• Keep car windows closed when traveling.

• Take vacations in areas where pollen is not as common, such as near the ocean.

• Give your child their allergy medicines, as prescribed by their healthcare provider.

• Reduce your child's time spent outdoors when the pollen count is high.

• Bathe and shampoo your child's hair after playing outside. Wash clothes that were worn outside.

• Don't rake leaves or have your child jump in piles of raked leaves during pollen season.

• Don't hang your child's bedding or clothing outside to dry.

• Have your child wear sunglasses and a hat when outside. This helps keep pollen out of their eyes and hair.

• Ask your child's healthcare provider if allergy testing and allergy immunotherapy are needed for your child. Allergy immunotherapy can give long-term relief of symptoms. It helps your child's body build up a resistance to pollen. Allergy immunotherapy can be given as a series of allergy shots. Tablets that dissolve under the tongue (sublingual immunotherapy) are also available to treat grass and ragweed allergies. Talk with your child's provider to learn if this is an option for your child.