Seasonal Allergies: Causes, Symptoms, and Best Drugs To Use

Published August 29th, 2021 by Chris Riley
Fact Checked by
Camille Freking
Medically Reviewed:
Dr. Angel Rivera

Season Allergies | Common Causes | Symptoms | Medications

If you notice that you experience nasal congestion, sneezing, and itchy, watery eyes around the same time every year, you may be suffering from seasonal allergies. Fortunately, there are many treatments available that can help control your symptoms.

What Are Seasonal Allergies?

Seasonal allergies are a type of allergic reaction that occurs in response to allergens that are only present in significant quantities at certain times of the year. Allergies occur when a person’s body mounts an excessive immune response against a substance that would otherwise be considered harmless, such as pollen. Substances that trigger an allergic reaction are known as allergens.

Some allergens, such as pollen, mold, and mildew, are more prevalent at certain times of the year than others. These allergens contribute to seasonal allergies. Perennial (year-round) allergies occur in response to allergens that are always present, such as dust mites and pet dander. It is possible for a person to suffer from both seasonal allergies and perennial allergies if they are allergic to multiple substances, which means they may experience symptoms year round and worsened symptoms during certain seasons, such as spring and fall.

What Are Some Common Causes of Seasonal Allergies?

Spring Allergies

Spring allergies are perhaps the most well-known type of seasonal allergies, but they aren’t necessarily limited to the spring. Depending on the part of the country you’re in, spring allergy symptoms can start to appear even in mid-winter if the temperatures are warm enough to allow plants, trees, grasses, and weeds to begin pollinating. The most common cause of spring allergy symptoms is pollen.

People may be allergic to many different types of pollen or only the pollen from a specific tree or plant. 

Trees that are known to trigger spring allergy symptoms include:

  • Alder
  • Aspen
  • Box elder
  • Cottonwood
  • Elm
  • Juniper
  • Mulberry
  • Olive
  • Pine
  • Sycamore
  • Ash
  • Beech
  • Cedar
  • Cypress
  • Hickory
  • Maple
  • Oak
  • Palm
  • Poplar
  • Willow

Grasses, weeds, and other plants known to contribute to spring allergy symptoms include:

  • Bermuda
  • Johnson
  • Orchard
  • Redtop
  • Sweet vernal
  • Fescue
  • June
  • Perennial rye
  • Saltgrass
  • Timothy

Most people find that they experience more symptoms when the pollen count for their specific allergen is high. Pollen counts increase throughout the spring season as the weather warms until summer, when the plants and trees are no longer flowering. Pollen counts are more likely to be high on windy days, while rainy days help to bring the pollen count down.

In addition to pollen, other common causes of spring allergies include mold and mildew both inside and outside the home. Mold and mildew grow more quickly in the warm, damp conditions that are common in the spring as a result of increasing temperatures and spring rain.

Fall Allergies

Fall allergy symptoms can begin as early as mid August. The biggest trigger for fall seasonal allergies is ragweed, a wild plant that is found across the United States but is especially prolific in the East and Midwest. Ragweed pollen can travel up to 400 miles, so even if you do not live in an area that has ragweed naturally, you may still be exposed to the allergen. The peak of ragweed season is early to mid-September, but the pollen is typically present from mid-August to November.

Other plants that are known to trigger fall allergies include:

  • Burning bush
  • Lamb’s-quarters
  • Sagebrush
  • Mugwort
  • Cocklebur
  • Pigweed
  • Tumbleweed
  • Russian thistle

Mold and mildew can also be more prevalent in the fall due to damp piles of leaves and compost, which provide a warm, moist environment for mold and mildew to proliferate. People with fall allergies should avoid creating leaf piles or compost piles near their homes and should dispose of leaves quickly in the fall season to avoid exposure to mold and mildew allergens.

What Are the Symptoms of Seasonal Allergies?

Regardless of the specific allergen that causes symptoms, seasonal allergies typically cause symptoms associated with a condition called allergic rhinitis. Allergic rhinitis is a term that is used to refer to a group of allergy symptoms that primarily affect the nasal passages. The symptoms are triggered when an individual inhales an allergen, such as pollen or mold spores.

The most common symptoms of allergic rhinitis include:

  • Runny nose
  • Sneezing
  • Itchy eyes
  • Itchy nose
  • Watery eyes
  • Coughing
  • Dark circles under the eyes
  • Scratchy throat

What Are the Best Drugs To Use for the Treatment of Seasonal Allergies?

There are many different types of drugs that are available for purchase over the counter or with a prescription for the treatment of seasonal allergies. Most of these drugs fall into one of three categories of medications: antihistamines, decongestants, or corticosteroids.


One of the most popular treatment options for seasonal allergies is antihistamines. Antihistamines are a class of medication that prevents allergy symptoms by blocking the action of histamine, a chemical in the body that is produced in response to allergen exposure.

When the body detects exposure to an allergen, it begins to mount an allergic response in people with allergies. The immune system prepares to defend the body against the perceived foreign substance and sends out chemicals called inflammatory mediators, which include histamines. These chemicals bind to receptors on cells throughout the body and deliver messages that result in allergy symptoms, such as increased mucus production, sneezing, itchy eyes, and more.

For example, respiratory allergens cause an inflammatory histamine response which results in symptoms in the nasal passages. 

Antihistamines work by binding to the histamine receptors on cells throughout the body. When the histamine is not able to attach to the cells, it is unable to deliver its message to start producing allergy symptoms. As a result, those with respiratory symptoms can start to breathe more easily with less nasal symptoms while those with hives may feel less itchy.

Antihistamines are commonly available in the form of liquids, tablets, or capsules. Some of the most well known antihistamines include diphenhydramine (Benadryl), loratadine (Claritin) and cetirizine (Zyrtec). The most common side effect of antihistamine use is drowsiness. Antihistamines work quickly to treat allergy symptoms, so they are best for treating acute symptoms that need quick relief. 


Decongestants are a class of medications that work to relieve congestion and swelling in the nasal passages. Unlike antihistamines, these medications are not used specifically for the treatment of allergies and may also be used for other illnesses, such as a sinus infection or cold. Decongestants work by narrowing the blood vessels that line the nasal passageways, which helps to reduce swelling, eases congestion, and makes it easier to breathe.

Like antihistamines, decongestants work quickly to treat allergy symptoms. Although they are effective for the treatment of acute symptoms, nasal decongestants should not be used for longer than three days, as they can cause a rebound effect that makes congestion worse when used for an extended period of time. Common decongestants include pseudoephedrine (Sudafed). Among the most common side effects of decongestants include headache, restlessness, and nausea or vomiting.


Corticosteroids are among the most effective treatments for seasonal allergy symptoms. Unlike antihistamines and decongestants, which work quickly, corticosteroids can take between two to four weeks to start providing maximum relief. Individuals suffering from seasonal allergy symptoms are able to use corticosteroid medications daily throughout the allergy season in order to prevent and treat symptoms of allergic rhinitis.

Corticosteroids work by preventing six different types of cells from producing the symptoms of an allergic reaction. As a result, corticosteroids can help reduce inflammation that often accompanies an allergic reaction. Corticosteroid nasal sprays have been shown to be more effective in the treatment of seasonal allergies than antihistamines.

Popular corticosteroid nasal sprays include medications like fluticasone (Flonase), budesonide (Rhinocort), and triamcinolone (Nasacort). Corticosteroid nasal sprays reduce inflammation in the nasal tissues, reducing congestion and helping patients to breathe more easily. The side effects most commonly associated with corticosteroid nasal sprays include stinging or burning in the nose, irritation or dryness in the throat, and an unpleasant taste in the mouth.


Seasonal allergies are caused by allergens that are present in high quantities only during certain seasons, such as spring or fall. Common causes of seasonal allergies include pollen, mold, and mildew. People experiencing allergic rhinitis as a result of seasonal allergies are likely to have symptoms that include nasal congestion, runny nose, sneezing, itchy or watery eyes, and more. Seasonal allergies can often be treated effectively with over-the-counter medications like antihistamines, decongestants, and corticosteroids.


Seasonal Allergies | Causes, Symptoms & Treatment | American College of Allergy, Asthma, and Immunology 

Steroids More Effective Than Antihistamines When Used As Needed For Allergies | ScienceDaily 

Allergic rhinitis | U.S. National Library of Medicine 

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