In most of the United States, spring allergies start in February and last until the early summer. However, these times may vary depending on the region and weather patterns.

Seasonal allergies, also called allergic rhinitis or hay fever, occur when the body’s immune system overreacts to a harmless substance, such as pollen, causing various symptoms. In addition to spring, some people experience allergies in the fall that can last from August to November.

In 2021, around 81 million people of all ages in the United States experienced seasonal allergic rhinitis.

Some people find the symptoms annoying, but for others, they can be debilitating, interfering with work, school, and everyday activities. The good news is that there are effective treatments, and people can minimize their seasonal allergy symptoms with planning.

Read on to learn more about when allergy season starts and how to manage seasonal allergies.

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In most of the mainland U.S., allergy season typically starts in early spring and can last through the fall. During this time, trees, grasses, and weeds release pollen into the air.

However, the timing of hay fever season varies depending on the location and types of plants present.

The length and severity of allergy season can also change from year to year. Factors such as temperature, rainfall, and wind patterns can all affect the amount of pollen in the air and how long it lingers.

People can have allergies to one or multiple types of pollen, and their symptoms depend on when plants release pollen. Therefore, anyone with seasonal allergies should check the local pollen count and stay aware of when pollen levels are high in their area.

Learn more about a pollen allergy.

Due to the varied geographical environments in different regions of the U.S., the onset of seasonal allergies may differ across the country. The timing of seasonal allergies also largely depends on weather conditions in any given area.

In much of the country, tree pollen is generally the first major allergen to cause symptoms, starting around February or March. Grass pollen usually follows in late spring or early summer, with ragweed being most common in August and September.

In tropical climates such as Florida and the Gulf Coast, people may experience seasonal allergies year-round as grass and other plants bloom throughout most seasons.

Furthermore, mild winter temperatures can cause plants to pollinate early, and heavy rain in spring can lead to rapid plant growth, which increases mold, causing symptoms that last into fall.

Ragweed is the most common cause of fall allergies, releasing pollen from August to November. It grows freely almost everywhere but is especially prevalent on the east coast and in the midwest.

Although the timing of allergy seasons varies, certain factors also influence how severe a person’s symptoms are, including:

  • cool nights and warm days, helping pollen thrive
  • heat and high humidity, encouraging mold
  • windy and warm days, allowing pollen counts to surge

Learn more about spring allergies.

Allergies can develop at any age, but allergic rhinitis often begins in children under 5 years of age. However, it becomes more common as children grow older. According to research, 8.5% of children ages 6–7 years have it, compared to 14.6% of those ages 13–14.

This data suggests that the risk of developing seasonal allergies increases as children enter adolescence.

It is important to note that while seasonal allergies increase with age, not everyone who develops them as a child will continue to experience them as an adult.

Some children may outgrow their allergies, while others may develop new allergies later in life. Genetics and environmental factors can also play a role in the development of allergies.

Learn more about allergies.

People with seasonal allergies should limit their contact with pollen as much as possible. They may need to stay indoors when the pollen count is high and close windows when necessary. Air conditioning can also help filter pollen from the air.

They can also take over-the-counter (OTC) and prescription medications to ease symptoms. These include:

  • Nasal corticosteroid sprays: These reduce inflammation in the nose and block allergic reactions.
  • Antihistamines: These relieve sneezing and itching of the nose and eyes.
  • Decongestants: These shrink the lining of the nasal passages and relieve stuffiness.
  • Leukotriene receptor antagonists: These block chemical messengers involved in allergic reactions.
  • Cromolyn sodium: This blocks histamine and leukotrienes, which are chemicals that cause allergy symptoms.

Learn more about treating seasonal allergies.

A person should contact their doctor if they experience severe seasonal allergy symptoms, such as:

The doctor may perform allergy testing to identify the source of the allergies and provide treatment options.

Additionally, if someone has seasonal allergy symptoms and OTC medications do not help, they should contact their doctor. They may need to start allergy shots or try a different type of medication to gain relief from symptoms.

Learn more about allergy testing.

Seasonal allergies typically start when the weather warms up and plants begin to bloom. For many areas, this means February onwards for tree pollen, followed by grass pollen, then ragweed in the late summer and fall.

However, when seasonal allergies start depends on the region, weather, and native plants.

People can manage their symptoms by limiting exposure to pollen when possible, taking OTC and prescription medications, and contacting their doctor when necessary.