Lettuce is a food which may result in allergy symptoms in sensitised individuals.

Lettuce Allergy Test: Allergen Exposure

Lettuce originated in the Mediterranean region, and has been recorded as being used for food as early as 400 BC. It is now probably the world’s most popular and well known salad vegetable and is cultivated across the globe.

There are a wide range of varieties of lettuce, including iceberg, cos, romaine and little gem, and the different variants can be classified according to whether the whole head or merely the leaves are harvested and served.

Its most common use – as leaves, but sometimes also as sprouted seeds – is in salads and sandwiches, but it may also appear in soups and stews. Edible oil is obtained from the tiny seeds, but extraction of the oil on any scale would not be feasible.

The sap of the plant contains lactucarium, which is used in medicine and folk medicine for its anodyne, antispasmodic, digestive, galactogogue, diuretic, hypnotic, narcotic, sedative, anaphrodisiac, carminative, emollient, febrifuge, hypoglycaemic, and parasiticide properties.

Lactucarium has effects similar to opium, although to a lesser degree, and unlike opioids it does not cause digestive upset or addiction. Normal doses can cause drowsiness, while excess doses cause restlessness, and overdoses can cause death through cardiac paralysis.

It is taken internally in the treatment of insomnia, anxiety, neuroses, hyperactivity in children, dry coughs, whooping cough, rheumatic pain, etc. The sap has also been applied externally in the treatment of warts.

Lettuce Allergy Test: Allergen Description

A lipid transfer protein present in lettuce has been characterised.

Lettuce Allergy Test: Potential Cross-Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected, as well as to a certain degree among members of the family Asteraceae.

A patient allergic to chicory reported reactions to the botanically related plants endive and lettuce. Additionally four patients with occupational contact dermatitis to lettuce were shown to be cross-reactive with endive.

Lettuce contains a lipid transfer protein (Lac s 1), which may result in cross-reactivity with other lipid transfer protein-containing foods.

Carrot shares allergens with lettuce, although carrot allergens are more potent than those of lettuce.

Lettuce Allergy Test: Clinical Experience

Lettuce allergy is not frequently reported in the literature, but is found in clinical practice, predominantly in the southern part of Europe. Lettuce may induce symptoms of food allergy, in particular oral allergy syndrome, in sensitised individuals. Adverse reactions may be severe, resulting in anaphylaxis.

Food-dependent exercise-induced anaphylaxis has been reported.

Generalised, pruritic, papular and erythematous eruption, associated with facial and lingual oedema and a tight throat, due to Lettuce, has been documented in a patient.

Previously unsuspected Lettuce allergy in a patient with delayed metal allergy has been reported.

Other reactions

Occupational eczema or contact dermatitis, combining delayed and immediate-type reactions, has been reported including contact hypersensitivity to Lettuce in a chef.

Greenhouse workers and gardeners are at risk of Compositae-related allergy to chrysanthemum, daisy and lettuce. Ingestion of lettuce was reported to result in lip and facial swelling, and in aggravation of pre-existing Compositae dermatitis