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North American genus of plants in the Asteraceae family; contain sesquiterpene lactones which cause a syndrome of abdominal pain, vomiting, diarrhea, incoordination, dyspnea. Includes H. amarum (H. tenuifolium), H. autumnale (sneezeweed, bitter weed), H. flexuosum (H. nudiflorum), H. hoopesii (orange sneezeweed), H. integrifolium, H. microcephalum (small head sneezeweed). H. amarum imparts a bitter taste to the milk of cattle which eat it. Called also Dugaldia spp., sneezeweed.