When the air is heavy with mold spores or pollens from trees, grasses, or weeds, about 35 million Americans experience sneezing, stuffy or runny noses and itchy, watery eyes. For some, allergies can also trigger asthma symptoms.

As we enter the spring sneezing season, here’s what you need to know about allergy timing, and how you can use that knowledge to feel better.

Seasonal timing

For most seasonal allergy sufferers, winter brings welcome relief. That’s because cold, dry air limits mold growth and most pollen-producing plants go quiet, at least for a while. There are exceptions: Molds in Florida and grass pollens in California persist year-round. And mountain cedar trees spew pollen through most of the winter in central Texas and some other parts of the Southwest.  Elsewhere, allergy season starts when trees resume growing and pollinating in the spring.

From an allergy standpoint, spring doesn’t necessarily start in March or at the same time everywhere. Instead, a northward march of rising tree pollen levels starts in the South, usually in January, and reaches more northern climes, including the Northeast, Midwest, and Pacific Northwest, often between mid-February and mid-March. As different tree species awaken from their winter rest, new pollens join the mix, extending tree pollen season through June in some places.

Meanwhile, grass pollens emerge between April and June and are shortly joined by weed pollens, which typically peak in late summer. In some places, grasses peak again in the late summer as well.

The first frost, which varies depending on where you live, puts an end to pollen season in most of the United States.

Warmer weather, more allergies

If you have seasonal allergies, you may have noticed that pollen seasons seem to start earlier these days. Studies confirm the change is real: Plants are releasing pollens earlier, starting with trees in the late winter and early spring. In the first decade of the 2000s, pollen seasons for trees, grasses, and weeds in the United States started an average of three days earlier than they did in the 1990s. A more recent study found that North American pollen seasons last an average of eight days longer than they did in the 1990s. The shift toward earlier, longer seasons is expected to continue.

Rising temperatures are to blame. Warmer weather in the winter and early spring jump start the growing seasons of pollinating plants, while later frosts in the autumn keep them going. Climate change also appears to be responsible for higher pollen levels in the air.

Taken together, the changes mean people are exposed to more allergy-causing substances for a longer time, something that may explain why seasonal allergies are becoming more common. Even older adults, once considered unlikely to develop new allergies, are becoming newly allergic at higher rates than in the past.

How to feel better

Use these tips to limit your exposure to pollens and molds when counts are high:

  • Keep your windows closed at night and, if possible, use air conditioning to clean, cool, and dry the air.
  • Keep windows closed and air conditioning on when you travel by car.
  • If you have severe symptoms but must be outside for long periods, wear a mask. The N95 and KN95 masks that effectively filter out viruses can also reduce your exposure to airborne allergens.
  • If you can, avoid mowing lawns or raking leaves, because those activities stir up pollen and mold spores.
  • If you do decide to do gardening or other lawn work, avoid touching your eyes and other parts of your face while outside.
  • After a long outdoor exposure, leave your shoes at the door and then take a shower, wash your hair, and put on fresh clothes.
  • In general, it’s smart for allergy sufferers to take their showers at night, so that they aren’t going to sleep with pollen on their skin and hair.
  • Don’t hang your sheets or clothes outside to dry.

Treatment timing

Talk to your doctor about a treatment plan. It may include medications in addition to limiting your exposure. One strategy may be to start some medications before pollen counts start to rise. For example, inhaled nasal steroids, a mainstay of treatment, take several days to start working, so it can be smart to begin using them a week or two before your symptoms typically start. If you have severe or long-lasting symptoms that are hard to control in other ways, you may be a candidate for allergy shots, which are injections that reduce your sensitivity. That can be a great long-term strategy but not a path to instant relief: It can take several months to see results.

Watching Patterns

You can’t control plant pollination or outdoor mold growth, but you can use your knowledge of seasonal patterns as a starting point to tackle allergy symptoms.

  • Symptom patterns. If you sneeze and rub your eyes only in early spring, a tree pollen allergy is a good guess. If you have symptoms from early spring through fall, you may well have allergies to several plant species. Year-round symptoms suggest you may have allergies to indoor substances, such as dust mites, or that you have a nonallergic form of rhinitis. The best way to confirm any hunches and get treatment advice: Get allergy skin testing from a board-certified allergist.
  • Pollen counts. While your nose may seem to know when pollen counts are rising, a better indicator is a count from the nearest station of the National Allergy Bureau, a network maintained by the American Academy of Allergy, Asthma and Immunology. You can sign up online, at pollen.aaaai.org, for alerts from your nearest station.
  • Weather. Even during peak pollen season, some days are better or worse than others. Dry, windy days mean higher pollen counts. Hot, humid weather encourages mold growth. On a rainy, windless day, pollens fall to the ground and stay put, giving many allergy sufferers a break (at least until the fallen pollen starts drying out and blowing around). A windy thunderstorm, on the other hand, can blow a lot of extra pollen through the air and cause symptom flare-ups.
  • Time of day. As a rule, pollen counts tend to be lightest during the morning, because, as sailors know, mornings are usually less windy than afternoons. So that can be a good time to get out for exercise or other outdoor activities.

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