Timothy grass pollen allergy
Phleum pratense
Timothy is a cool-season hay and pasture grass found in all 50 states. It is one of the common northern grasses whose summer pollen can cause hay fever.
What it is
Timothy (Phleum pratense) is a cool-season perennial bunchgrass that grows 20 to 40 inches tall.1 It is Eurasian in origin. It was found growing in New Hampshire in 1711, and from 1747 it spread from New England to Canada and westward.1 Today it grows in all 50 states and is cultivated for hay and pasture throughout North America.1
Timothy is one of the common northern grasses behind grass allergy, along with Kentucky blue, rye and fescue.3 ACAAI also names it among the wind-pollinated grasses most likely to cause seasonal allergic reactions.7 Its pollen can cause hay fever and skin irritation (dermatitis).2
Many grass pollens cross-react with one another.5 The overlap between temperate grasses such as timothy and subtropical grasses is incomplete. In nasal challenge tests on a small number of patients in Florida, timothy and Bahia grass pollen did not cross-react.4
Symptoms it causes
Breathed in, grass pollen such as timothy can cause sneezing, a runny or stuffy nose, an itchy nose and facial pressure.3 It can also make the eyes itchy, red and watery. In people with asthma, it can bring on coughing, wheezing, chest tightness and shortness of breath.3 Less often, direct contact with grass causes itchy, raised welts (hives).3
Some people with grass pollen allergy get an itchy or swollen mouth, lips or throat after eating certain raw foods, including peaches, celery, tomatoes, melons and oranges. This is oral allergy syndrome.6 It is generally mild. Rarely, it causes severe throat swelling, and very rarely a reaction that affects the whole body (anaphylaxis).6
Where and when it grows
Timothy grows best in nutrient-rich soil in cool, humid climates, and it does not tolerate drought.2 It is widely cultivated in the northeastern states south to the Cotton Belt, and in the humid Puget Sound region and mountain areas.1 In Ohio it can be found almost everywhere, including crop fields, meadows, roadsides and orchards.2
It flowers from June to September, depending on altitude and latitude.1 Reported flowering runs from June to July in Ohio and North Dakota, June to August in Montana, and June to September in Colorado and Wyoming.1 Ohio’s weed guide places it in June and early July.2
For comparison, grasses as a group pollinate in late spring in most US regions, from about April through early June.3
Cross-reactions
| Can also react to | What happens |
|---|---|
| Other grass pollen | An AAAAI expert answer notes that there is significant cross-reactivity between many grass pollens.5 |
| Bahia and Bermuda grass pollen | Cross-reactivity between temperate grasses such as timothy and subtropical grasses such as Bahia and Bermuda is incomplete. In nasal challenge tests on a small number of patients in Florida, timothy and Bahia pollen did not cross-react.4 |
| Raw peach, celery, tomato, melon and orange | Some people with grass pollen allergy get an itchy or swollen mouth, lips or throat after eating these foods raw (oral allergy syndrome).6 |
Symptoms it can cause
When to get help
See an allergist if
- Allergy symptoms last for several months of the year
- Allergies bring repeated sinus problems, a blocked nose or trouble breathing
- Over-the-counter remedies don’t control your symptoms
- Allergies or asthma get in the way of daily life
- You often wheeze, cough at night or after exercise, or feel short of breath
Based on ACAAI’s “When To See an Allergist”. General information, not medical advice.
Questions
Is timothy grass the same plant as timothy hay?
Yes. Timothy is cultivated for both hay and pasture throughout North America, so timothy hay is cut from the same grass.1
When does timothy grass release pollen?
It flowers from June to September, depending on altitude and latitude. Flowering is usually June to July in Ohio and North Dakota, June to August in Montana, and June to September in Colorado and Wyoming.1
Does timothy grow in the South?
It is found in all 50 states, but it is cultivated mostly from the northeastern states south to the Cotton Belt, and in the humid Puget Sound region and mountain areas.1
Sources
- Phleum pratense. USDA Forest Service, Fire Effects Information System. Read on October 15, 2026.
- Timothy (Phleum pratense). Ohio State University, Ohio Perennial and Biennial Weed Guide. Read on October 15, 2026.
- Mowing Down Your Grass Allergies. American Academy of Allergy, Asthma and Immunology. Read on October 15, 2026.
- The molecular allergology of subtropical grass pollen. Molecular Immunology (author manuscript, QUT ePrints). Read on October 15, 2026.
- Grass pollen immunotherapy mixtures. American Academy of Allergy, Asthma and Immunology, Ask the Expert. Read on October 15, 2026.
- Oral Allergy Syndrome (OAS) or Pollen Food Syndrome. American Academy of Allergy, Asthma and Immunology. Read on October 15, 2026.
- Gardening with Allergies. American College of Allergy, Asthma and Immunology. Read on October 15, 2026.