Ragweed is a flowering plant that comes from the sunflower family. Unfortunately, once this plant takes root in a given area, it is very difficult to completely rid the area of ragweed. While many people regard spring as prime pollen season, one type of pollen wreaks havoc in the late summer and fall. Ragweed pollen usually reaches peak levels in mid-September; this type of pollen can cause seasonal allergic rhinitis (more commonly known as hay fever), which affects as many as 23 million Americans. There are 17 species of ragweed in the United States. The weeds grow in most regions, typically blooming and producing a fine-powder pollen from August into November.


Why Are People Allergic to Ragweed?

The flower of the ragweed plant typically blooms from early July until the weather gets colder. One ragweed plant can release as many as a billion pollen grains. Ragweed pollen grains are very small. At approximately 19-20 microns in diameter (or 1/25,000th of an inch), these grains are microscopic (humans can usually see no smaller than 40 microns). Goldenrod is often mistaken for ragweed, but goldenrod does not release pollen into the air. Instead, goldenrod is pollinated by insects and so is typically not an allergenic plant. Those who suffer from ragweed pollen allergies are said to suffer from ‘hay fever’.

When small grains of pollen are ingested or inhaled, the body recognizes these particles as foreign entities. One in seven people have bodies that ‘overdo’ the immune response to these pollen grains. Their bodies mount an immune response by releasing antibodies into the body’s system and by creating a large inflammatory response (with chemicals from within the body such as histamine). The effects of these responses include runny nose, swollen and teary eyes, coughing, increase in mucus production, sneezing, itchy eyes and skin, swollen nasal passages, rashes and hives. Some people may even suffer from asthma.


Management and Treatment

If you’re suffering from hay fever symptoms in the late summer or fall, consult an allergist about the possibility of a ragweed allergy. Your allergist can confirm a diagnosis with a skin test — applying a diluted allergen to the surface of your skin and waiting about 15 minutes to see if there is a reaction, such as a raised red bump that itches.

Ragweed allergies can be treated with antihistamines and other allergy medications. As with pollen season in the spring, you can try to get ahead of these allergies by starting your medication two weeks before you expect your symptoms to be at their worst. Ask your allergist whether any of your medications can be taken before symptoms develop.


Two immunotherapy options are available for severe cases of ragweed allergy:

  • Allergy shots can help your body build resistance.
  • Tablets that dissolve under your tongue are available by prescription. Pills must be started 12 weeks before the beginning of ragweed season.

Other tips include:

  • To avoid pollen, know which pollens you are sensitive to and then check pollen counts. In spring and summer, during tree and grass pollen season, levels are highest in the evening. In late summer and early fall, during ragweed pollen season, levels are highest in the morning.
  • Keep your windows closed at all times, both at home and in the car.
  • Remember that pollen can be tracked into your home via your clothes, your hair or your pet — so change your clothes after being outside for long periods of time, shower before going to bed and wash your hands after petting an animal that has been outside.

- College of Allergy, Asthma, & Immunology

Schedule an Indoor Air Quality appointment 

Fall allergy season is a great time to schedule an IAQ appointment. Not only does regular preventative maintenance keep your HVAC system healthy, service will help reduce indoor allergens and ensure your system is dust and blockage free.