What does it mean to have a lectin (lectin) allergy, specifically an adverse reaction to lectin, a type of carbohydrate-binding protein?

From the Guidelines

Being allergic to lectin means your immune system overreacts to these proteins found in many plant foods, particularly legumes, grains, and certain vegetables, leading to adverse health effects such as digestive issues, skin rashes, or respiratory problems. When you consume foods containing lectins, your body may respond with allergic symptoms ranging from mild digestive issues like bloating, gas, and diarrhea to more severe reactions such as skin rashes, respiratory problems, or in rare cases, anaphylaxis 1. Common lectin-rich foods include beans, lentils, peanuts, tomatoes, potatoes, and whole grains. Management typically involves avoiding or reducing consumption of high-lectin foods or preparing them in ways that reduce lectin content, such as soaking, sprouting, fermenting, or pressure cooking beans and grains.

Key Considerations

• Lectin sensitivities are often considered food intolerances and may involve different immune mechanisms, unlike true food allergies which involve IgE antibodies 1.
• If you suspect a lectin allergy, it's essential to consult with an allergist or immunologist for proper testing and diagnosis before making significant dietary changes, as eliminating lectin-containing foods could potentially lead to nutritional deficiencies since these foods provide important nutrients 1.
• A food allergy is defined as an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food, and food allergens are those specific components of food or ingredients within food that are recognized by allergen-specific immune cells and elicit specific immunologic reactions 1.

Diagnosis and Management

• Diagnosis of food allergy, including lectin allergy, requires documentation of a clinical history of a food allergic reaction, and testing includes a food-specific IgE test and/or skin prick tests 1.
• All food-allergic patients should be prescribed antihistamines for mild reactions and an epinephrine autoinjector device for severe reactions, and comprehensive counseling regarding food allergy is crucial for management 1.

From the Research

Definition of Lectin Allergy

• A lectin allergy refers to an adverse reaction to lectin, a type of carbohydrate-binding protein found in various foods and substances 2.
• Lectins can cause nutrient deficiencies, disrupt digestion, and lead to severe intestinal damage when consumed in excess by individuals with dysfunctional enzymes 2.

Mechanism of Lectin Allergy

• The binding properties of lectins can lead to cross-reactivity with body tissues, resulting in the production of antibodies against lectin and bacterial antigens, followed by autoimmunity 2.
• The detection of immunoglobulin G (IgG) or immunoglobulin A (IgA) antibodies against specific lectins may serve as a guide for the elimination of these lectins from the diet 2.

Role of Lectins in Allergic Sensitization

• Lectins play a crucial role in allergic sensitization and allergic disease, with carbohydrates on allergens and their counterstructures on antigen-presenting cells (lectins) being highlighted as key factors 3.
• The interplay between lectins and other determinants of allergenicity can lead to TH2 cell differentiation and the production of deleterious specific IgE antibodies 3.

Lectin Receptors and Allergic Inflammation

• C-type lectin receptors (CLR) and other lectin receptors, such as galectins and sialic acid-binding immunoglobulin-type lectins, form the largest receptor family among pathogen recognition receptors 4.
• These receptors can recognize both foreign and endogenous molecules, and play an important role in innate and adaptive immunity, as well as in the regulation of allergic inflammation 4.

Galectins and Allergic Disorders

• Galectins are members of the animal lectin protein family, with binding specificity for β-galactoside sugars, and are known to be expressed in various effector cells of the immune system 5.
• Galectins have multiple roles in innate and adaptive immunity, and can exert immuno-regulatory activities, enroll in tissue inflammation, and regulate immune homeostasis 5.