The risk factors

A personal allergic profile

In allergic individuals, there is a type of antibody called IgE which recognises the allergens to which the individual is sensitive. These antibodies then trigger inflammation upon contact.

Some individuals will be more likely to develop an allergic response due to having a genetic predisposition. This genetic predisposition is called atopy. It has been demonstrated that familial predisposition exists also and is called the "atopic" profile which makes it possible to determine the risk of allergic symptoms in children¹.

A proven hereditary risk

The risk of developing a respiratory allergy is greater in allergic families¹ as shown below:

Changes in the environment and lifestyles, increasing urbanisation, pollution, tobacco use or passive smoking (second-hand smoke) and changes in our eating habits are all factors that promote the development of allergies.

Atmospheric pollution aggravates respiratory disease

Atmospheric pollutants are not the cause of allergic symptoms but they appear as aggravating factors.  

Several recent studies using different methods to measure atmospheric pollution demonstrate a link between pollution, respiratory allergies and asthma². Moreover, the risk of dying from a respiratory disorder is 3 times higher in major cities with high concentrations of ozone than in those with lower levels³.

The environment as modifier of the immune system

A recent study⁴ demonstrated that exposure of women to farm products during pregnancy could indicate a natural immuno-modulation model which alters the immune system of babies.

Other studies⁵ have suggested that high levels of germs, toxins and substances relating to farm animals, stables, consumption of untreated milk were inversely associated with the onset of asthma in children. However, the findings are not only related to the type of exposure and/or lifestyle but also each individual's genetic heritage.

Numerous specialists give credence to the hygiene hypothesis in explaining changes in allergies: overly protected during childhood due to minimal exposure to external pathogenic agents, the immune system turns against all the proteins common to daily life.

According to the same theory, some studies^6,7 have demonstrated the protective role of "rural" life (including specific conditions such as the proximity of animals or an inferior level of hygiene) or conversely a higher risk related to excessive administration of medication from the earliest age (such as early use of antibiotics⁸).

¹ Polonovski J-M.et al. Rhinite allergique. Impact Internat. 1999, p.109-111
² Patel MM. et al. Air pollution and childhood asthma: recent advances and future directions. Current Opinion in Pediatrics 2009; 21:235-242
³ Jerrett M. et al. Long-term ozone exposure and mortality. N Engl J Med. 2009 Mar 12; 360(11):1085-95
⁴ Schaub B.et al. Maternal farm exposure modulates neonatal immune mechanisms through regulatory T cells. J Allergy Clin Immunol. 2009 Apr; 123(4):774-82.e5
⁵ Von Mutius E. Clinical Reviews in allergy and immunology. J Allergy Clin Immunol 2009; 123:3-11
⁶ Liu et al. J Allergy Clin Immunol. 2003; 111; 471-8
⁷ Strachan DP. Hay fever, hygiene, and household size, BMJ, 1989 Nov 18; 299(6710):1259-60
⁸ Foliaki S. et al. Antibiotic use in infancy and symptoms of asthma, rhinoconjunctivitis and eczema in children 6 and 7 years old: International Study of Asthma and Allergies in Childhood Phase III. J Allergy Clin Immunol.2009 Nov; 124(5):982-9.