Skin Allergy to Lettuce Or Carrots

Lettuce (Lactuca sativa or iceberg lettuce) contains lactucopicrin and lactuciin. These allergenic substances belong to a group of compounds known as sesquiterpene lactones (SQLs), a large and diverse group of biologically active plant constituents.

Lettuce (a member of Asteraceae plant family) and carrot (a member of the Apiaceae plant family) have been found related in that carrots share many allergens with lettuce. Although carrot allergens are more potent than those of lettuce. These findings may have some importance in patients with food-related symptoms, such as atopic dermatitis, because lettuce, when included in their diets, may aggravate the underlying disease.

Various sesquiterpene lactones are known to be toxic to human and animal parasites, insects and vertebrates. Many of these compounds or plants containing them are a cause of allergic contact dermatitis in humans but some of them have been used for their pharmacological activity. Sesquiterpene lactones also act as plant growth regulators and are responsible for allelopathic properties of many plants. Various activities of sesquiterpene lactones suggest their evolutionary significance in plants as deterrents against herbivores and anti-fungal, anti-bacterial allelopathic agents.