Lettuce is in the Asteraceae family of plants, other plants in this family include sunflower seeds, tarragon, artichoke and camomile.

Lettuce contains one allergenic protein called Lac s 1, it is a Lipid Transfer Protein (LTP), these proteins are resistant to heat and are found in many types of plants. People suffering from a more severe allergy to cooked fruit may be sensitised to this group of proteins.

Lettuce also contains a contact allergen called lactucarium which can cause skin irritation. This is the white milky fluid found in the base of the stems when the plant is picked.

Lettuce is a low FODMAP food. FODMAP stands for Fermentable oligosaccharides, disaccharides, monosaccharides and polyols. Foods high in FODMAPs can cause symptoms of food intolerance, affecting the gastro intestinal system and this can be mistaken for a true IgE food allergy.

Lettuce is one of the few fresh foods that contains a moderate amount of sulphites. Sulphites are inorganic salts used in preservations and have the potential to cause symptoms of food intolerance to those sensitive to sulphites, this food intolerance is more common in asthmatics. An improvement in symptoms can be made with a change to a low sulphite diet.

Most lettuce varieties have a moderate amount of salicylates (iceburg lettuce are low in salicylates). salicylates have the potential to cause worsening of asthma, swelling, itching and hives as well as food intolerance symptoms in people who are sensitive to salicylates.

You can read more about Food Intolerances on the dedicated Food Intolerance Page.

You may be suffering from LTP Syndrome if you have reactions to various fruits, vegetables and nuts and your reactions continue to be severe after you have discarded the peel and have cooked the food.

Lettuce is also commonly linked to allergic contact dermatitis.

Common foods involved in LTP allergy include kiwi, strawberries, sunflower seeds, walnut, apple, mulberry, banana, pea, apricot, cherry, plum, almond, peach pomegranate, raspberry, tomato, grape, celery, peanut, asparagus, cabbage, broccoli, chestnut, lemon, tangerine, orange, hazelnut, lettuce, lentils, lupin, green bean, pear, mustard, wheat and maize.

Other plants which may cause a cross reaction on contact are chicory and endives.

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