Phadia, a manufacturer of allergy medications, notes that there are more than 100 varieties of lettuce throughout the world. Of these, several plants within the lettuce family — including mugwort and ragweed — release pollen that can cause allergic reactions. In addition, lettuce is also a food allergy for some people, and eating it can lead to an array of allergic symptoms.
Food Allergies
A food allergy, notes the Cleveland Clinic, takes place when your body's immune system responds in a defensive manner to a particular food protein, even though this protein isn't harmful to your body. When you first ingest an allegen, your immune system will create antibodies specific to that food, which will then cause the release of histamines when you eat the same food again. These histamines try to expel the protein from your body. Symptoms of food allergies can vary widely depending on the severity of the allergy and the type of food to which you're allergic. And, they may occur immediately or even several hours after ingestion. Symptoms of an allergic reaction include tingling in the mouth, a swollen tongue, vomiting, skin rashes or hives, stomach cramps, diarrhea and, in severe cases, anaphylaxis, which may be fatal if left untreated.
Lettuce Allergies
The AllAllergy website references a number of studies in which eating lettuce led to allergic reactions, with symptoms including oral allergy syndrome, angioedema, rhinitis, anaphylaxis, dermatitis and nasal obstruction. A study published in a 2009 issue of the "Journal of Investigational Allergology and Clinical Immunology" examined two subjects who experienced anaphylaxis after eating lettuce to try to isolate the allergen that was causing the reaction. Researchers were able to isolate the allergen in lettuce, which they determined is a lipid transfer protein called Lac s 1.
Ragweed
Allergies to the variety of lettuce known as ragweed are typically not food allergies. Rather, they occur when you inhale the plant's pollen when it flowers. In an article in "Allergic Living," writer Dory Cerny notes that symptoms of a ragweed allergy can range from mild eye irritation and a runny nose to complete sinus congestion, sleep problems and itchy eyes, nose and throat. Ragweed, she writes, can also exacerbate asthma, and has been linked to ear infections in children and sinusitis in adults.
Ragweed Allergens
According to a study published in the December 2005 issue of "International Archives of Allergy and Immunology," ragweed pollen represents the largest single source of allergenic protein in the United States. This study examined the spectrum of allergens found in ragweed, and determined that ragweed pollen contains a pan-allergen called profilin. In addition, researchers also concluded that ragweed contains calcium-binding proteins that can cause "extensive cross-reactivity" in people who are sensitive to pollen. If you are allergic to ragweed, your doctor may prescribe pre-season immunotheraphy, which involves receiving injections containing tiny amounts of the allergen, which can desensitize you to ragweed's allergic effects.
References
- International Archives of Allergy and Immunology: The Spectrum of Allergens in Ragweed and Mugwort Pollen
- Allergic Living; Get A Grip On Ragweed Allergy; Dory Cerny
- Journal of Investigational Allergology and Clinical Immunology; Lettuce-Induced Anaphylaxis. Identification of the Allergen Involved
- Cleveland Clinic: Food Allergies
- Phadia: Lettuce
- All Allergy: Lettuce
