Slide show: Poison ivy and other summer skin irritants
Photo of ragweed plant and rash
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Ragweed plants usually grow in rural areas or open meadows. Ragweed pollen is a primary cause of hay fever (allergic rhinitis). For those who are sensitive to ragweed, ragweed exposure can also cause a rash. You might notice small, itchy bumps and blisters. A ragweed rash usually develops within two days of exposure and resolves on its own within two to three weeks, as long as you avoid any additional ragweed exposure. In the meantime, control itching with an over-the-counter anti-itch cream, such as hydrocortisone cream. Consult your doctor if the rash is painful or lasts longer than three weeks.

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