What Is Ragweed?
Ragweed is a weed that grows all over the United States. It’s especially common in the Eastern and Midwestern states, and Alaska is the only state where it doesn’t grow. It triggers ragweed allergy symptoms in many people.
Ragweed is an annual plant, so it grows for only one season. The plants start to grow in the spring, then flower in August or September in most parts of the U.S..
The particles of pollen from ragweed plants are tiny and easily carried around by the wind. A single ragweed plant can produce a billion grains of pollen.
What does ragweed look like?
Ragweed plants have spiky flowers that are dull green or yellowish, and the stems of the plant look hairy. The leaves are thin and divided, with lobes or “teeth” somewhat like fern leaves. Many branches grow from each stem of a ragweed plant.
Types of ragweed
Ragweed is part of the aster (asteraceae) family, which also includes daisies and sunflowers. Seventeen types of ragweed plants grow in North America. Among the species that are most common in the U.S. are common ragweed and giant ragweed.
Common ragweed grows 1 to 3 feet tall, and its leaves look fern-like. Giant ragweed can grow from 3 to 12 feet tall, and its leaves are usually divided into three to five lobes.
Ragweed vs. goldenrod
Goldenrod is another plant that’s part of the aster family, and it blooms around the same time as ragweed. Goldenrod and ragweed plants look somewhat similar, so people sometimes confuse the two. But if you have allergy symptoms, they're most likely triggered by ragweed, not goldenrod. While it's possible to be allergic to goldenrod, its pollen isn't distributed through the air. So you'd have to have physical contact with the plant to trigger a reaction.
You can tell the two plants apart because goldenrod has bright yellow flowers that look fluffier than ragweed flowers, which are duller in color. And goldenrod has a single stem with the flowers concentrated at the top, while ragweed has more branches growing from the sides of the stem.
Because goldenrod pollen is heavier than that of ragweed, the wind can’t carry it away. Goldenrod is a perennial plant, which means it grows back every year, and it’s important for pollinators.
Ragweed map
Ragweed allergies are usually the worst in Eastern and Midwestern states, where the allergy season can last up to four months. In some Southern states, the ragweed season is shorter.
The most common ragweed species vary depending on the area.
What Is a Ragweed Allergy?
A ragweed allergy is an allergic reaction to the pollen of the ragweed plant. When you have an allergic reaction, it’s because your immune system perceives the pollen as a harmful substance that it needs to fight off. So your body releases a chemical called histamine that causes symptoms like sneezing and a runny nose.
If your allergies flare up in the late summer or early fall, you’re probably allergic to ragweed. It’s the most common trigger for hay fever.
How common are ragweed allergies?
About 1 out of 5 people have allergic reactions to ragweed when levels of its pollen in the air are high. In the U.S., almost 50 million people have ragweed allergy. Among environmental allergens, ragweed is one of the most common.
Ragweed season
Ragweed allergy season starts when ragweed plants are in bloom and releasing pollen and ends when cooler weather kills the plants. For most of the U.S., the season starts around July or August, peaks in mid-September, and lasts through October. For some areas in the South, including parts of Texas and Louisiana, ragweed allergy season is usually between August and November. Florida has the shortest season, from August to October.
In some areas, ragweed allergy season has gotten longer. This may be because of climate change, according to the U.S. Environmental Protection Agency.
Ragweed Allergy Causes
It's not clear why some people are allergic to ragweed and others aren't. But exposure to the plant's pollen is what triggers allergy symptoms. Ragweed grows in many areas, and its pollen spreads easily, so you may be unaware that you’ve been exposed.
The allergy symptoms are actually caused by the histamine your body releases in reaction to ragweed pollen, not the pollen itself.
Ragweed allergy risk factors
You might have a higher risk of ragweed allergy if you have:
- A history of asthma
- A history of eczema
- A family history of allergies
Living in an area with high levels of ragweed pollen may also make you more likely to have a ragweed allergy.
Ragweed Allergy Symptoms
If you have a ragweed allergy, your symptoms may include:
- Runny nose or nasal congestion
- Sneezing
- Coughing or itchy throat
- Postnasal drip (when mucus runs down your throat, which can cause a sore throat)
- Itchy, watery, or red eyes
- Fatigue or disturbed sleep
- Rash or hives
When you have symptoms like this in reaction to a seasonal pollen, it’s called seasonal allergy rhinitis, or hay fever.
Ragweed rash
Sometimes, exposure to ragweed pollen can cause allergy symptoms on your skin in the form of hives or a rash. This is called ragweed rash. When you have ragweed rash, you might have itchy red streaks that may also be painful and later form blisters. You can get this rash 24 to 48 hours after being exposed to ragweed pollen, and it might last two to three weeks.
Severe ragweed allergy symptoms
The symptoms of ragweed allergy can range from mild to severe. A little bit of a stuffy nose can be a nuisance, but if you’re really congested and constantly coughing or sneezing, these more serious symptoms could get in the way of your everyday activities.
If you have asthma and breathe in ragweed pollen, it can make your lungs and airways inflamed and swollen and lead to an asthma attack. You might have serious symptoms like:
Wheezing
Pain or tightness in your chest
Shortness of breath
Coughing
Ragweed Allergy Diagnosis
If you think you have a ragweed allergy, talk to your doctor about your symptoms. They'll probably do a physical exam and ask about your health history and symptoms.
To confirm a ragweed allergy diagnosis, an allergist can do a skin prick or scratch test. This involves applying a small amount of ragweed pollen to your skin, scratching or pricking your skin with a needle, then waiting about 15 minutes to see if you have a reaction. If you have a ragweed allergy, your skin will become red, itchy, or swollen where the pollen was applied.
Another way allergists can diagnose ragweed allergy is by testing your blood for antibodies against ragweed pollen.
Ragweed Allergy Treatment
If allergy testing confirms that you have a ragweed allergy, your doctor may recommend over-the-counter (OTC) or prescription medications or allergy shots.
Medications for ragweed allergy treatment include:
- Antihistamines such as fexofenadine, which ease ragweed allergy symptoms by blocking histamine
- Decongestants such as pseudoephedrine, which relieve nasal congestion
- Nasal corticosteroids such as fluticasone, which reduce inflammation and congestion
- Leukotriene inhibitors such as montelukast (Singulair), which block another chemical your body releases in response to an allergen
Your doctor also may recommend immunotherapy, or allergy shots, to treat ragweed allergy. Over the course of months or years, allergy shots help your body develop a tolerance to ragweed so it no longer triggers an allergic reaction. Another immunotherapy option is tablets you put under your tongue, which work the same way allergy shots do.
The best ragweed allergy medicine for you depends on the symptoms you have and how serious they are. If your symptoms are mild, for example, an over-the-counter antihistamine may be enough. But certain treatments may work better for some people than for others.
Sometimes, early treatment can help minimize ragweed allergy symptoms. If your doctor recommends this approach, you can start taking medications two weeks before ragweed season starts. That way, you can stop your allergic reactions before they start.
Living With Ragweed Allergies
Because ragweed grows abundantly, avoiding it may be impossible. But there are ways to limit your exposure and lower your risk of ragweed allergy symptoms.
During ragweed allergy season, you should:
Check pollen counts. Limit the time you spend outdoors when ragweed pollen levels are high.
Avoid peak ragweed hours. Limit the time you spend outside between 10 a.m. and 3 p.m. Ragweed pollen counts are lower in the early morning and late afternoon.
Keep windows closed. At home and in the car, don’t open the windows. Using central air conditioning with a HEPA filter will keep you cool and help filter out pollen.
Consider wearing a face mask and hat when you’re outside. This can reduce the amount of pollen you breathe in and keep pollen from settling in your hair.
Change your clothes and wash your hands after you've been outside. Ragweed can stick to skin and clothing.
Avoid drying laundry outside. Ragweed pollen can settle on your laundry. Instead, dry your laundry in a dryer or on indoor racks or lines.
Try to reduce the pollen that comes into your home. Take your shoes off indoors to avoid tracking pollen in, and don't wear clothes to bed that you’ve worn for long periods outside.
How to track the ragweed pollen count
You can check ragweed pollen levels through the National Allergy Bureau, websites such as the American Academy of Asthma, Allergy, and Immunology, and through various pollen tracking apps. Some newspapers, local news sites, weather websites, and air quality monitoring sites also provide current or forecasted pollen levels. Some of these resources may provide a general pollen level — like low, medium, or high — rather than a specific number for the pollen count.
Ragweed allergy foods to avoid
For some people with ragweed allergies, eating foods that contain proteins similar to those found in ragweed pollen can worsen allergy symptoms. Possible triggers are:
- Bananas
- Melons
- Cucumber
- Zucchini
- Sunflower seeds
- Chamomile tea
When this happens, it’s called oral allergy syndrome (OAS) or pollen food allergy syndrome (PFAS). It can cause a tingly or itchy feeling in your mouth. Talk to your doctor if you think you may have this syndrome, and they can help figure out which foods to avoid.
Ragweed Facts
Here are some things to know about ragweed:
Ragweed pollen travels easily. Because it's so light, the wind carries ragweed pollen a long way. Researchers have found ragweed pollen 2 miles up in the atmosphere and 400 miles out at sea.
Ragweed often grows along roadsides, in vacant lots, and along rivers.
Warm, breezy weather and humidity help release ragweed pollen.
Ragweed is worse when nights are cool and days are warm and dry.
The pollen season for ragweed and other weeds is usually from about July to October, while the pollen seasons for trees and grasses happen at other times of the year.
Some ragweed allergy symptoms are similar to cold symptoms, like stuffy or runny nose, sneezing, and coughing. If you have both asthma and a ragweed allergy, it can cause severe symptoms.
Takeaways
Ragweed allergy is very common in the late summer and fall. It happens when your immune system overreacts to the pollen of the ragweed plant, which grows abundantly in most areas of the U.S. it's hard to completely avoid exposure to this weed, but there are ways to reduce your exposure as well as treatments that can ease your allergy symptoms.
Ragweed Allergy FAQs
How do you know if you have ragweed allergy?
Seasonal allergy symptoms can be similar to cold symptoms. To find out for sure whether you have a ragweed allergy, you can get a blood or skin test from an allergist.
In what month is ragweed the highest?
In most areas of the U.S., the height of ragweed allergy season is in September.
What is the best thing to take for ragweed allergies?
You can treat ragweed allergies with over-the-counter or prescription medications or allergy shots. But a treatment that works well for someone else may not work for you. Your doctor can recommend the best treatments for you to try.
What are the worst states for ragweed allergies?
States in the East and Midwest are typically the worst for ragweed allergy.
What is mistaken for ragweed?
Goldenrod is often mistaken for ragweed. It blooms at the same time of year and the two plants look somewhat alike. But goldenrod's pollen doesn't spread through the air, so it's much less likely to trigger allergies.
Where is ragweed most commonly found?
Ragweed is found all over the U.S.. It often grows on the side of the road, in riverbanks, and in vacant lots.
Why are ragweed allergies so bad?
One reason ragweed allergies are so bad is because ragweed pollen spreads easily and travels far, making it difficult to avoid. Some researchers say ragweed allergy season has become longer because of climate change.
How to get rid of ragweed?
If you have ragweed growing in your yard, you can pull it out. But wear gloves because ragweed can irritate your skin.
