Ragweed

Ragweed plants bloom in the United States in late summer, usually beginning in August, and into the fall. Ragweed pollen is one of the main causes of hay fever. Hay fever also is called allergic rhinitis.

For people who are allergic to ragweed, coming in contact with the plant pollen through touch or through the air also can cause a rash. This condition is called allergic contact dermatitis. The rash often includes itchy red streaks on the skin and swelling of the eyelids. A ragweed rash usually appears within two days of coming in contact with the plant. It typically goes away within three weeks, as long as there's no more contact with ragweed.

To soothe the rash, use a cream that eases itching that you can buy without a prescription, such as hydrocortisone cream. An antihistamine medicine that you buy without a prescription also can be helpful. Talk to your health care professional if the rash is painful or if it lasts longer than three weeks.