Table 1.

Factors influencing the development and expression of allergic diseases [4, 5, 11, 18]

Host factors

Genetics:

genes predisposing to atopy, e.g. FCR1A (Fc fragment of IgE, high affinity receptor for alpha subunit) genes predisposing to airway hyperreactivity, e.g. DARC (Duffy antigen/receptor for chemokines) genes directly modulating responses to environmental exposures, e.g. CD14, Toll-like receptor 4 polymorphism genes regulating the immune response, e.g. IL (interleukin) 13, STAT6 (signal transducer and activator of transcription 6) genes determining the tissue response to chronic inflammation, e.g. ADAM33 (A disintegrin and metalloproteinase domain-containing protein 33), PDE4D (phosphodiesterase 4D)

Obesity: body mass index (BMI) > 30 kg/m2

Male sex in childhood

Inhaled environmental factors

Allergens:

Indoor, e.g. mites, animal dander (dogs, cats, mice), cockroaches, fungi, moulds, yeasts Outdoor, e.g. pollens, fungal spores

Outdoor/indoor air pollutants: CO (carbon monoxide), CO2 (carbon dioxide), NO (nitrogen dioxide), SO2 (sulphur dioxide), PAHs (polycyclic aromatic hydrocarbons), O3 (ozone), particulate matter (PM)

Infectious agents (predominately viral)

Tobacco smoke: passive smoking: maternal prenatal smoking, postnatal environmental tobacco smoke exposure; active smoking

Occupational sensitizers, e.g. flour, soybean dust, wood dust, grain dust, formaldehyde

Non-inhaled environmental factors

Foods, e.g. peanuts, tree nuts, wheat, soy, egg

Ticks, Hymenoptera

Occupational sensitizers, e.g. nickel, platinum, vanadium salts

Diet