Sesquiterpene lactones are a class of chemical found in many plants that can cause allergic reactions. Some plants containing these compounds are:

• Chrysanthemum
• Pyrethrum
• Ragweed
• Sneezeweed
• Sagebrush
• Wormwood
• Mugwort
• Boneset
• Poverty weed
• Marsh elder
• Cockebur
• Burdock
• Chamomile
• Artichoke
• Gailladrin
• Parthenium
• Sunflower
• Lettuce
• Spinach

Artemesinin, a new, highly-effective anti-malarial compound, is a sesquiterpene lactone found in Chinese wormwood. Lactucin, desoxylactucin, lactucopicrin, lactucin-15-oxalaat, lactucopicrin-15-oxalaat are some of the most prominent and well determinable sesquiterpene lactones found e.g. in lettuce and spinach, giving most of the bitter taste in these crops.