Causes

Seasonal Allergy Causes Overview

Seasonal allergies are very common: about one in four U.S. adults has a diagnosed seasonal allergy (CDC). The most common type is hay fever, also called allergic rhinitis.

Hay Fever

Hay fever happens when the immune system overreacts to an allergen, most often pollen. Despite the name, it isn’t caused by hay and doesn’t cause a fever (ACAAI).

While hay fever will show cold-like symptoms, viruses like the cold don’t actually cause hay fever. Commonly, allergens appear as pollens from plants that are wind-pollinated such as:

• Trees
• Seasonal grasses
• Weeds
• Ragweeds

Pollens that are carried by insects are too heavy and won’t stay in the air for long, so they don’t cause many allergic responses.

Common Seasonal Allergy Symptoms

The symptoms of seasonal allergies are much like those of dust or pet allergies. They include:

• Sneezing
• Runny nose
• Itchy, watery, or swollen eyes
• Itchy throat and ear canals
• Ear or nose blockage
• Postnasal drainage

Some people, especially those with asthma, may also have:

• Wheezing
• Tight chest
• Headache
• Cough
• Shortness of breath
• Fatigue

People with asthma may have flare-ups during allergy season. Symptoms usually last as long as you are exposed to the allergen and return with each exposure.

Origin and Causes of Seasonal Allergies

As said earlier, hay fever can be triggered by seasonal plants, pollens, and other foreign things that overwhelm the immune system. When the immune system is allergic to a particular substance, it signals it as dangerous, although it might not be. In response to this, the body will release histamines and other chemicals into the blood. These chemicals then produce the effects we know as allergies.

Spring

Tree pollen is usually the first to appear, often starting in late winter or early spring, followed by grass pollen in late spring. Timing varies by region (ACAAI). In northern areas, many people react to birch pollen.

Other trees that produce allergens in North America are:

• Alder
• Cedar
• Horse chestnut
• Poplar
• Willow
• Birch

It’s also important to note, a rainy spring can cause molds and fungus to grow, making spores. When this happens, spores will create problems for people who are sensitive to them.

Summer

Grasses pollinate mainly in late spring and summer, and weeds in late summer and fall (ACAAI). Common culprits include:

Weeds

• Ragweeds
• Cockleweed
• Tumbleweed
• Pigweed
• Russian thistle
• Sagebrush

Grasses

• Blue grasses
• Bermuda
• Orchard
• Red top
• Sweet vernal
• Timothy

Ragweed is one of the most well-known and widely spread allergens in summer and fall. Even if they are not near where you live, the tiny pollens can fly far in the air to reach you. This is because the pollen is so small it can move through the air with ease.

Air pollution: Ground-level ozone and other pollution, often higher on hot, sunny summer days, can irritate the airways and make allergy and asthma symptoms worse.

Fall

Ragweed is the biggest fall trigger. It grows throughout much of the U.S., especially in the East and Midwest, and releases pollen from late summer until the first frost (ACAAI).

Other plants that drop pollen in the fall time are:

• Burning bush
• Cocklebur
• Lamb’s-quarters
• Nettles
• Pigweed
• Sagebrush and mugwort
• Mugworts
• Sorrels
• Tumbleweed and Russian thistle
• Fat hens
• Plantains

Winter

Winter brings relief to those with allergic symptoms liked hay fever. This is in part because, in winter, outdoor allergens may become inactive. It’s also due to people spending more time indoors in the cold months. If you are sensitive to seasonal allergies, however, indoor allergens like pet dander, dust mites, mold, or bugs may trigger effects.

Seasonal Allergy Diagnosis

If your symptoms happen only at certain times of year, you likely have seasonal allergic rhinitis. A doctor or allergist can confirm it, often with skin or blood tests, and identify your specific triggers (ACAAI).

Knowing your triggers helps you time treatment and reduce exposure, for example by starting medicine before your pollen season begins.

Prevention and Treatment of Seasonal Allergies

There are many ways to treat seasonal allergies, all of which depend on their severity, however, the best way is to help stop them is by:

• Reducing exposure to certain pollens
• Staying indoors when there are high allergens counts
• Washing hands and bathing often
• Closing windows and using air conditioning
• Wearing a mask outdoors on high-pollen days if it helps you

Common treatments are:

• Antihistamines
• Decongestants
• Nasal sprays
• Inhalers (for allergic asthma)
• Corticosteroid nasal sprays

If medicines aren’t enough, doctors may suggest allergy shots or tablets. This immunotherapy gradually makes the immune system less sensitive to allergens (Mayo Clinic).

Conclusion

Seasonal allergies can be uncomfortable to live with, so talk to a doctor if you think you have any. They will listen to your symptoms and test you to give an official diagnosis. After that, they will advise you on what actions to take to prevent effects. Lastly, they may give you prescription drugs or point you towards over-the-counter medications.

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Written by: Madiha Ather Hashmi (November 08, 2020)

This article is for general education and is not medical advice. Talk with your doctor or pharmacist about your symptoms and before starting, stopping, or combining any medicine.

Seasonal Allergy Cause FAQs

What causes seasonal allergies?

Mostly wind-borne pollen from trees, grasses and weeds, plus outdoor mold spores (ACAAI).

Why don’t flowers usually cause hay fever?

Most showy flowers have heavy pollen carried by insects, which doesn’t stay airborne long.

When is ragweed season?

From late summer until the first frost (ACAAI).

Can you get seasonal allergies in winter?

Outdoor pollen is low, but indoor allergens like dust mites, pet dander and mold can cause symptoms.

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