Author: Hon A/Prof Marius Rademaker, Dermatologist, Hamilton, New Zealand, 2002.

Common name: Lettuce
Botanical name: Lactuca sativa (milk sap)
Family: Asteraceae (Compositae)
Origin: Lettuce originates from the wild Lactuca serriola found in the Mediterranean and Near East (Persia).
Description: All lettuce cultivars such as Cos, Leaf, Butterhead and Iceberg are regarded as being variants of Lactuca sativa. Lettuce has been transformed from an erect plant with bitter leaves to various cultivars including ones with distinctive heads of chlorophyll deficient leaves. The common and Latin name derive from the milky sap (latex) found in all parts of the plane {lac, lactis = milk}. The latex has a milky sedative effect and lettuce has been grown as an herb. {Note: there is no cross-reaction between lettuce latex and natural rubber latex}.
Uses: A large number of different cultivars of lettuce have been bred and are now grown all over the World, mainly for use in salads.
Allergens: Lactucin, lactucopicrin (?sesquiterpenes)
Allergy: Lettuce is an occasional cause of allergic contact dermatitis particularly in food handlers, chefs and market gardeners. It tends to cause hand dermatitis, which spreads up the forearms. Unfortunately immediate hypersensitivity to lettuce has also been reported. This includes Urticaria and life threatening anaphylaxis. The allergy seems to cross react with chicory and endives so these vegetables may need to be avoided as well. It is a form of Compositae allergy so may also cross react with other members of this large plant family.
Cross reactions: Chicory and endives
Other information: Paintings of what appear to be Cos Lettuce have been found in Egyptian tombs dating back to as early as 4500 BC although there is some uncertainty about their identity. The first authenticated records of cultivated lettuce date back to Greek historical records in 450 BC. In the first century AD the Romans were growing a number of different cultivars.
Patch test: Leaf as is, sesquiterpene lactone mix

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