When most people think of seasonal allergies, they think of grass and tree pollen in the spring. In the fall, there’s another pollen that is just as common and bothersome to people with allergies — ragweed pollen. Ragweed season begins in early August and peaks in mid-September and October before declining in November.
Ragweed pollen allergy is a leading cause of seasonal allergic rhinitis (also called hay fever), which affects more than 23 million people in the United States. Ragweed pollen can be found in every state in the United States plus Canada.
What is ragweed allergy?
Ragweed is an allergen for people allergic to ragweed. Ragweed pollen is made of tiny particles that float through the air and cause allergy symptoms in people who are allergic to ragweed. Of all ragweed allergy symptoms, cough, runny nose, and an itchy throat are the most common.
What is ragweed pollen?
Ragweed pollen is a powdery substance that consists of tiny particles, or grains. The grains of pollen help fertilize other ragweed plants. One ragweed plant can produce up to 1 billion pollen grains that can float through the air, and either produce seeds or end up in your nose, eyes or mouth, causing great discomfort if you’re allergic to it. Pollen can also collect on clothes, hair and the skin.
What is ragweed?
Ragweed plants are weeds that grow wild almost everywhere, abundantly in the east and Midwest. Many are weeds, shrubs and herbs. They are often found in suburban and rural areas.
Most ragweed plants are annuals, meaning they live just one year. They start to emerge in the spring and flower in mid-August in most parts of the country.
Warm temperatures, reduced humidity and breezy conditions create the ideal environment for ragweed plants to release pollen.
People who have ragweed allergies are reacting to its pollen. During ragweed season, one plant can release a billion grains of it into the air.
What are symptoms of ragweed allergies?
Like all pollen allergies, allergies to ragweed can lead to seasonal allergic rhinitis (hay fever), inflammation of the nasal passages. For people with a ragweed allergy, exposure to the plant by touch or through airborne particles can lead to them developing a ragweed rash.
Other common ragweed allergy symptoms are:
- Nasal congestion
- Runny nose with thin, water discharge
- Postnasal drip
- Watery, itchy or irritated eyes
- Eye swelling – the “allergic shiner”
- Weakness or fatigue
- Hives on the skin
What does ragweed rash look like?
A person who has been exposed to ragweed pollen may notice itchy red streaks appearing on their skin 24 to 48 hours after exposure. The rash can be painful and may form into blisters.
Ragweed rash can last anywhere from two to three weeks and will usually improve on its own.
Can ragweed cause an asthma attack?
Ragweed pollen can cause asthma symptoms to flare up. When a person with asthma and ragweed allergy inhales ragweed pollen, it can cause the lungs and airways to become inflamed and swollen. The muscles around your airways tighten and spasm as more mucus that usual is produced, making it harder to get air into your lungs. All these factors can lead to increased coughing, wheezing and shortness of breath — classic signs of an asthma attack.
People with allergic asthma will require treatment for their asthma symptoms, but they may also require treatment for their allergies.
If you have allergic asthma, use your prescribed quick-relief albuterol inhaler the first moment you notice symptoms. This medication relaxes the muscles that surround the airways, making it easier to breathe within a few short minutes. Using a quick-relief inhaler at the first sign of symptoms can help prevent symptoms from getting out of control. However, if you think you are experiencing a severe asthma attack, it’s best to also call 9-1-1 and seek immediate care.
Controlling your ragweed allergy can also help control your asthma. The best strategy to prevent an allergic asthma flare is to avoid ragweed pollen. Check ragweed pollen counts online in your area so you know when to avoid going outside as much as possible. Talk with your doctor about adjusting your Asthma Action Plan during ragweed season.
When is ragweed allergy season?
Ragweed allergy season begins in early August in most parts of the country. When does ragweed bloom? Generally, mid-September is when ragweed pollen counts are usually at their highest. Warm temperatures, reduced humidity and breezy conditions create the ideal environment for ragweed plants to release pollen.
Ragweed season typically lasts 6-10 weeks, ending by early November or when temperatures drop below freezing for a few weeks.
Keeping an eye on weather forecasts, sudden changes in temperature, daily ragweed pollen counts and air quality alerts can help you anticipate when to avoid outdoor activities and reduce exposure to allergens and irritants.
Airborne pollen concentrations are usually highest in the morning, just after the dew dries and on into late morning. High levels can last until late afternoon.
Ragweed pollen is so light and airy that it can travel great distances — even as far as 400 miles in one case. So even if you live in an area with few ragweed plants, you could still suffer from exposure to ragweed.
Check out our Asthma and Allergy Forecast to get up-to-date information on the pollen allergy risk in your local area.
Visit the National Allergy Bureau at AAAAI.org/nab to check the pollen count for ragweed in late summer and fall. You can also visit the U.S. Environmental Protection Agency’s airnow.gov website for air quality alerts. Both websites also have apps available for smartphones and tablets.
Ragweed pollen is believed to be one of the primary reasons for the September Asthma Peak – a time in mid-September when asthma-related hospitalizations spike. It happens soon after children go back to school and are exposed to more allergens as well as respiratory illnesses.
What plants cause ragweed season?
Ragweed hails from the genus Ambrosia in the aster family. There are about 50 species of Ambrosia and they are native to North America. The most widespread species is Ambrosia artemisiifolia.
Most ragweed is annual, meaning that it flowers and dies in one season. Where does ragweed grow? These plants can grow anywhere but they are mostly nondescript. They typically have deep roots in the ground. Ragweed comes in two types:
- Common ragweed plants have a fern-like appearance and are often found in many yards and gardens. They grow about 3.5 feet high and include a series of thin leaves usually positioned opposite each other.
- Giant ragweed plants (called Ambrosia trifida) grow between 3 to 17 feet high. They are less fern-like in appearance and have 3-5 lobes of leaves.
It’s the smaller, tooth-leaved ragweed that lives in low grass that is the primary source of allergens. The tall goldenrod species shares its seasonal bloom with ragweed and is often blamed for pollen problems, but these plants are not ragweed.
You may need to avoid certain fruits and vegetables if you re allergic to ragweed and develop symptoms from eating these foods. This happens because foods botanically related to ragweed can trigger what is known as oral allergy syndrome (OAS).
Foods in the ragweed family include:
- melon (watermelon, cantaloupe, honeydew)
- sunflower seed
Are there any treatments for ragweed allergies?
Over-the-counter and prescription allergy medications, including antihistamines and anti-inflammatory nasal sprays, can help relieve symptoms and treat ragweed allergies. If you know your allergies are worse in late summer and early fall, start taking your allergy medications two weeks before symptoms are at their worst. Talk with your doctor about which medication is best for you.
Ragweed immunotherapy is available to help build tolerance to allergens, reducing or eliminating symptoms. Ragweed pollen immunotherapy is available in two forms:
- Allergy shots: can combine one or multiple allergens in one injection, administered weekly in a doctor’s office.
- Under-the-tongue tablets: a daily tablet that dissolves under the tongue, available for grass and ragweed pollen; administered 3 months prior to or during allergy season.
Talk with a board-certified allergist to determine if immunotherapy is right for you.
How can I minimize the impact of symptoms during a ragweed season?
- Pre-medicate with an antihistamine and/or corticosteroid nasal spray 2 hours prior to allergen exposure. For eye allergies, use eye drops as needed.
- Avoid ragweed pollen. In late summer and early fall, levels are highest in the morning. Pollen can also surge on windy, warm days and after a thunderstorm or rainfall. Limit time outside when pollen counts are high – usually in the mornings through early afternoons.
- Change clothes when coming inside.
- Wear a mask when doing outdoor activities and raking leaves. Find a mask designed to filter pollen and keep it from reaching your nasal passages.
- Monitor ragweed pollen counts. Airborne pollens can travel for several miles.
- Keep windows and doors shut at your home; close windows of your car while driving.
- Take a shower, wash your hair and change your clothes after time outside.
- Dry laundry indoors rather than on a clothesline outdoors.
If you have allergic asthma that is affected by an allergy to ragweed, talk with your doctor about adjusting your Asthma Action Plan or treatment plan in the late summer and fall. Be sure to take your daily asthma medications as prescribed – even during the summer when you may experience fewer symptoms – and avoid exposure to ragweed when possible.
Talking About the Weather
What's the spring allergy outlook where you live? Will sudden temperature changes trigger an asthma flare? Weather can play a key role in allergy and asthma symptoms, as well as flu transmission. Allergy & Asthma Network partnered with Weather Trends International to provide forecasting and analysis for people with asthma and allergies. It compiles information about an area's temperature, anticipated pollen forecast, flu prevalence, and more in determining its forecast.
Are there other conditions that can look like or complicate allergies
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Purvi Parikh, MD, is an adult and pediatric allergist and immunologist at Allergy and Asthma Associates of Murray Hill in New York City. She is on faculty as Clinical Assistant Professor in both departments of Medicine and Pediatrics at New York University School of Medicine.
Peyton Eggleston, MD, is a board-certified pediatric allergist and immunologist in Baltimore, Maryland. He is professor emeritus at Johns Hopkins Children’s Center.