Table 2 Current definitions of conditions covered by the allergy specialty and updated to the new ICD-11 “Allergic and hypersensitivity conditions” chapter

Rhinitis

Rhinitis is an inflammation of the nasal mucosa clinically characterized by major symptoms: sneezing, nasal pruritus, running nose, and stuffy nose.

Allergic and hypersensitivity disorders involving the respiratory tract

 Allergic rhinitis

Allergic rhinitis is an inflammation of nasal airway triggered by allergens to which the affected individual has previously been sensitized. Pathogenesis of allergic rhinitis is type I IgE-mediated allergy on the nasal mucosa. Antigens inhaled into sensitized nasal mucosa bind to IgE antibodies on mast cells, which release chemical mediators such as histamine and leukotrienes. The main triggers are inhaled allergens, such as house dust mites and pollens.

 Non-allergic rhinitis

Non-allergic rhinitis is an inflammation of nasal mucosa in which allergic mechanisms are not involved. It covers many different phenotypes and the major symptoms (sneezing, running nose, and stuffy nose) with variable intensity according to the triggers/causes.

Asthma

Asthma is a clinical syndrome characterized by recurrent attacks of breathlessness and wheezing or cough, which vary in severity and frequency from person to person. In an individual, they may occur from hour to hour and day to day. Allergic and non-allergic asthma are a heterogeneous group of disorders due to inflammation of the air passages in the lungs and affects the sensitivity of the nerve endings in the airways so they become easily irritated.

 Allergic asthma

Allergic asthma is the most easily recognized asthma phenotype, which often commences in childhood and is associated with a past and/or family history of allergic disease such as eczema, allergic rhinitis, or food or drug allergy. Examination of the induced sputum of these patients before treatment often reveals eosinophilic airway inflammation. The main triggers are inhaled allergens, such as house dust mites and pollens. Patients with this asthma phenotype usually respond well to inhaled corticosteroid (ICS) treatment depending on the severity.

 Non-allergic asthma

Non-allergic asthma occurs in some patients who have asthma that is not associated with allergy. The cellular profile of the sputum of these patients may be neutrophilic, eosinophilic or contain only a few inflammatory cells (paucigranulocytic). Patients with non-allergic asthma often respond less well to ICS. It can cover different phenotypes, such as Aspirin induced asthma, virus induced asthma, exercise induced bronchospasm.

Conjunctivitis

Conjunctivitis is the inflammation of the conjunctiva. It can have many different causes and can cover both allergic and non-allergic conjunctivitis. Allergic conjunctivitis is an IgE-mediated response due to the exposure of seasonal or perennial allergens in sensitized patients. The allergen-induced inflammatory response of the conjunctiva results in the release of histamine and other mediators. Symptoms consist of redness (mainly due to vasodilation of the peripheral small blood vessels), edema (swelling) of the conjunctiva, itching, and increased lacrimation (production of tears). Besides IgE-mediated conjunctivitis, contact allergic conjunctivitis involving TH1 mechanisms also occurs.

Allergic or hypersensitivity disorders involving the eye

Dermatitis

Local inflammation of the skin, that can cover both immune-mediated and non-immune mediated conditions.

Allergic or hypersensitivity disorders involving skin and mucous membranes

 Contact dermatitis

Allergic contact dermatitis is an eczematous response provoked by a type IV delayed immune reaction in the skin to a substance or substances to which the individual has previously been sensitized.

Non-allergic contact dermatitis is usually due to external irritants; it is an eczematous reaction provoked by acute or prolonged and repeated contact with a substance or substances which are injurious to the skin. Common irritants include defatting agents (solvents, soaps and detergents), acids (both inorganic and organic) and alkalis (e.g., sodium hydroxide and wet cement).

 Atopic eczema

A chronic inflammatory genetically determined eczematous dermatosis associated with an atopic diathesis (elevated circulating IgE levels, Type I allergy, asthma and allergic rhinitis). It is manifested by intense pruritus, exudation, crusting, excoriation and lichenification. Often presenting in infancy affecting the face, forearms and lower limbs, it tends to move to the limb flexures after infancy. Although commonly limited in extent and duration, it may be generalized and life-long.

Urticaria (or Spontaneous urticaria)

Urticaria is a disease characterized by the development of wheals (hives), angioedema, or both. It is classified as acute when it lasts less than six weeks, and chronic when lasts six weeks or more. When the reaction is mediated by immunological mechanisms, the term should be allergic urticaria.

Anaphylaxis

Anaphylaxis is a severe, life-threatening systemic hypersensitivity reaction which is rapid in onset with potentially life-threatening airway, breathing, or circulatory problems and is usually, although not always, associated with skin and mucosal changes. It can be allergic or non-allergic.

Anaphylaxis

Food hypersensitivity

Food hypersensitivity reactions are adverse effects of food or food additives that clinically resemble allergy. Food allergy is an adverse reaction to food mediated by an immunologic mechanism, involving specific IgE (IgE-mediated), cell-mediated mechanisms (non-IgE-mediated) or both IgE- and cell-mediated mechanisms (mixed IgE- and non-IgE-mediated).

Complex allergic or hypersensitivity conditions

Drug hypersensitivity

Drug hypersensitivity reactions are the adverse effects of pharmaceutical formulations (including active drugs and excipients) that clinically resemble allergy. It belongs to type B adverse drug reactions, which are defined by the World Health Organization as the dose-independent, unpredictable, noxious, and unintended response to a drug taken at a dose normally used in humans. It covers many different clinical phenotypes with variable onset and severity.

Hymenoptera and other insects hypersensitivity or allergy

Hymenoptera and other insects’ hypersensitivity cover local cutaneous reactions (large local reactions) and anaphylaxis due to contact to the venom (sting, bite) or saliva (bite) of insects (e.g., bee, wasp, tick). These reactions can be immune mediated (e.g., IgE-mediated or non-IgE-mediated venom allergy) or non-immune mediated.