WHAT IS FOOD ALLERGY?
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.
WHAT ARE FOOD ALLERGENS?
Food allergens are defined as those specific components of food or ingredients within food (typically proteins, but sometimes also chemical haptens) that are recognized by allergen-specific immune cells and elicit specific immunologic reactions, resulting in characteristic symptoms.
Some allergens (most often from fruits and vegetables) cause allergic reactions primarily if eaten when raw. However, most food allergens can still cause reactions even after they have been cooked or have undergone digestion in the stomach and intestines.
A phenomenon called cross-reactivity may occur when an antibody reacts not only with the original allergen, but also with a similar allergen. In food allergy, cross-reactivity occurs when a food allergen shares structural or sequence similarity with a different food allergen or aeroallergen, which may then trigger an adverse reaction similar to that triggered by the original food allergen.
Cross-reactivity is common, for example, among different shellfish and different tree nuts.
Food oils—such as soy, corn, peanut, and sesame—range from very low allergenicity (if virtually all of the food protein is removed in processing) to very high allergenicity (if little of the food protein is removed in processing)
WHAT IS THE DIFFERENCE BETWEEN FOOD ALLERGY AND FOOD INTOLERANCE?
Foods or food components that elicit reproducible adverse reactions but do not have established or likely immunologic mechanisms are not considered food allergens. Instead, these nonimmunologic adverse reactions are termed food intolerances
For example, an individual may be allergic to cow’s milk due to an immunologic response to milk protein, or alternatively, that individual may be intolerant to milk due to an inability to digest the sugar lactose.
In the former situation, milk protein is considered as an allergen because it triggers an adverse immunologic reaction.
Inability to digest lactose leads to excess fluid production in the gastrointestinal (GI) tract, resulting in abdominal pain and diarrhea
This condition is termed lactose intolerance, and lactose is not an allergen because the response is not immune based.
WHAT ARE THE MANIFESTATIONS OF FOOD ALLERGIES?
Food-induced anaphylaxis
GI food allergies and several specific syndromes
− Immediate GI hypersensitivity
− Eosinophilic esophagitis (EoE)
− Eosinophilic gastroenteritis
− Food protein-induced allergic proctocolitis (AP)
− Food protein-induced enterocolitis syndrome (FPIES)
− Oral allergy syndrome (OAS)
Cutaneous reactions to foods
− Acute urticaria
− Angioedema
− The increase in atopic dermatitis (AD) symptoms
− Allergic contact dermatitis
− Contact urticaria
Respiratory manifestations
Heiner syndrome
WHAT ALL THINGS CAN COEXIST WITH FOOD ALLERGY?
ASTHMA
ATOPIC DERMATITIS
EOSINOPHILIC ESOPHAGITIS
EXERCISE INDUCED ANAPHYLAXIS
WHAT ARE THE RISK FACTORS FOR DEVELOPING FOOD ALLERGY?
Family history of atopy and presence of atopic dermatitis
WHO ARE AT RISK OF DEVELOPING FOOD ALLERGY?
Patients at risk for developing food allergy are defined as those with a biological parent or sibling with existing, or history of, allergic rhinitis, asthma, atopic dermatitis, or food allergy.