Is allergy increasing?--early life influences

Area of Science:

• Epidemiology
• Immunology
• Allergology

Background:

• Global prevalence of allergic conditions (allergic rhinitis, asthma, eczema) has risen significantly since the mid-20th century.
• Elevated immunoglobulin E (IgE) levels correlate with increased incidence of allergic diseases, suggesting an immune system shift.
• Atopy (allergic predisposition) is influenced by early life events, including intrauterine and infant exposures.

Purpose of the Study:

• To explore the hypothesis that changes in the intrauterine environment and infancy (e.g., nutrition, infection rates) contribute to the observed increase in atopy and allergic diseases.

Main Methods:

• Review of epidemiological data and existing studies on allergic condition prevalence and IgE levels.
• Analysis of factors influencing immune system development in early life, such as the intrauterine environment, nutrition, and infection exposure.
• Hypothesizing potential mechanisms linking early life exposures to T-helper 2 (TH2) cell development and subsequent atopic disease.

Main Results:

• Epidemiological data show a clear increase in allergic conditions and IgE levels over recent decades.
• The intrauterine environment appears to promote TH2 cell development and IgE production, potentially predisposing to atopy.
• Reduced early-life infections, possibly due to modern healthcare, may be associated with increased atopy, potentially via reduced T-helper (TH) responses.

Conclusions:

• Changes in intrauterine and infant environments, including nutritional factors and infection rates, are plausible explanations for the rise in atopy and allergic diseases.
• Early life immune programming, particularly the balance between TH1 and TH2 responses, is critical in the development of allergic conditions.
• Further research into specific environmental and lifestyle factors during early development is warranted to understand and potentially mitigate the increasing burden of allergic diseases.