• 22 Jun, 2026
• SendClinic
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What Causes Seasonal Allergies | SendClinic

When the Seasons Change, So Does How You Feel

Every spring, millions of people start sneezing, rubbing their eyes, and reaching for tissues. You might feel fine all winter, then suddenly feel miserable the moment trees start to bloom. If this sounds familiar, you are probably dealing with seasonal allergies. You are far from alone — seasonal allergies affect a large portion of the population in the United States each year.

Understanding why seasonal allergies happen can help you feel less frustrated and more in control. Once you know what is triggering your symptoms, you can take steps to feel better. This article breaks down the causes of seasonal allergies in simple, easy-to-understand terms.

What Are Seasonal Allergies?

Seasonal allergies are also called allergic rhinitis, or sometimes “hay fever.” Despite that name, hay is rarely the cause, and a fever is not usually a symptom. The name stuck over the years, but the condition is really about your immune system reacting to things in the air around you during certain times of the year.

Your immune system is designed to protect your body from harmful things like bacteria and viruses. With seasonal allergies, the immune system makes a mistake. It treats harmless substances — like pollen from trees or grass — as if they were dangerous invaders. This triggers a reaction in your body that causes the symptoms you feel, like sneezing, a runny nose, itchy eyes, and congestion.

Seasonal allergies are different from year-round allergies, which are called perennial allergies. Year-round allergies are often triggered by indoor things like pet dander, dust mites, or mold. Seasonal allergies tend to flare up at specific times of year, depending on what plants are releasing pollen in your area.

The Main Culprit: Pollen

Pollen is the number one cause of seasonal allergies. Pollen is a tiny powder that plants release as part of their reproduction process. It is so small and light that it floats easily through the air. When pollen lands in your nose or eyes, your immune system may react and cause allergy symptoms.

Different plants release pollen at different times of year. Trees tend to release pollen in the early spring. Grasses usually pollinate in the late spring and early summer. Weeds, including the notorious ragweed, release pollen in the late summer and fall. This is why some people only have symptoms in the spring, while others suffer more in the fall.

Ragweed is one of the most common allergy triggers in North America. A single ragweed plant can release billions of pollen grains in one season. Ragweed pollen can also travel hundreds of miles in the wind, which means even people in cities with few plants can be exposed. Knowing which plants trigger your allergies can help you plan ahead during peak seasons.

Why Your Immune System Overreacts

When a person with seasonal allergies breathes in pollen, their immune system releases a chemical called immunoglobulin E, or IgE. This antibody then triggers the release of another chemical called histamine. Histamine is the main chemical responsible for allergy symptoms. It causes blood vessels to expand, tissues to swell, and nerves to become irritated — which leads to sneezing, itching, and a runny nose.

Not everyone’s immune system reacts this way to pollen. Scientists believe that both your genes and your environment play a role. If one or both of your parents have allergies, you are more likely to develop them too. However, having a family history of allergies does not mean you will definitely get them, and people without any family history can still develop allergies.

It is also worth noting that allergies can develop at any age. Some people have seasonal allergies their entire lives. Others develop them as adults, even if they had no symptoms as children. The reasons for this are not completely understood, but changes in your immune system, environment, and even where you live can all play a role.

What Makes Symptoms Worse

Even if you have allergies, some days feel much worse than others. Several factors can make your symptoms more intense. Pollen counts are higher on warm, windy days because the breeze carries pollen far and wide. Rainy days often bring relief because rain washes pollen out of the air. Spending time outdoors during peak pollen hours — usually mid-morning — can also increase your exposure.

Air pollution can make allergy symptoms worse too. Studies suggest that pollutants in the air can irritate the airways and make the immune system more sensitive to pollen. This is one reason why people living in urban areas sometimes have more severe allergy symptoms, even when pollen levels are similar to rural areas.

Certain behaviors can also affect how bad your symptoms get. Keeping windows open during high pollen days lets pollen into your home. Exercising outdoors on high pollen days can cause you to breathe in more pollen because you are breathing faster and deeper. Simple changes in your daily habits can make a real difference during allergy season.

How Seasonal Allergies Are Different from a Cold

Many people confuse seasonal allergies with the common cold because the symptoms can look very similar. Both can cause a runny nose, congestion, and sneezing. However, there are some key differences. Colds are caused by viruses, while allergies are caused by your immune system reacting to pollen. Colds often come with a fever, body aches, and a sore throat — symptoms that are not typical with allergies.

Another big difference is how long symptoms last. A cold usually goes away within seven to ten days. Allergy symptoms can last for weeks or even months, as long as the pollen that triggers them is in the air. Allergy symptoms also tend to improve quickly when you move indoors or away from the pollen source.

If you are not sure whether you have a cold or allergies, a healthcare provider can help you figure it out. SendClinic makes it easy to connect with a licensed provider from your phone or computer — no insurance required and no waiting room needed. Getting the right answer early means you can start feeling better sooner.

Taking the Next Step Toward Relief

Seasonal allergies can make you feel worn out, foggy, and miserable. But understanding what causes them is the first step toward managing them. Pollen from trees, grasses, and weeds triggers an overreaction in your immune system, and that reaction produces the symptoms that make allergy season so uncomfortable for so many people.

There are many options available to help manage seasonal allergy symptoms. A healthcare provider can help you find the right approach based on your specific triggers and how severe your symptoms are. If you are struggling with allergy symptoms and want guidance, SendClinic offers convenient video and phone visits with licensed providers who can help you get on the right track.

You do not have to white-knuckle your way through every allergy season. With the right information and support, you can take back control and enjoy the seasons again.

References

• Asthma and Allergy Foundation of America. “Rhinitis (Nasal Allergies).” AAFA. 2022.
• Wheatley, Lisa M., and Alkis Togias. “Allergic Rhinitis.” New England Journal of Medicine. 2015.
• National Institute of Allergy and Infectious Diseases. “Allergic Diseases.” NIH. 2023.
• Centers for Disease Control and Prevention. “Allergies and Hay Fever.” CDC. 2023.
• Platts-Mills, Thomas A.E. “The Allergy Epidemics: 1870–2010.” Journal of Allergy and Clinical Immunology. 2015.