Lettuce and carrot allergy: are they related?

Lettuce is commonly included in many elimination diets of subjects with either food allergy or atopic dermatitis since IgE-mediated allergic reactions have not been reported. We have observed a positive carrot skin test and/or RAST in two clinically lettuce sensitive, ragweed allergic subjects and positive lettuce skin test and/or RAST in two ragweed allergic patients with oral allergy syndrome to carrot. In this study lettuce allergy and the allergenic relationship between iceberg lettuce (Lactuca sativa L.), a member of the Asteraceae and carrot, a member of the Apiaceae, were investigated using sera from those four individuals. SDS-PAGE immunoblotting results indicated that iceberg lettuce can induce an IgE-mediated response. Fourteen allergens were detected between 13 and > 113 kD. RAST inhibition demonstrated that carrot does share common 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.