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.
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