Changes that may have contributed to the rise in allergic disease

I. Increased exposure to perennial indoor allergens

Increased time spent indoors (1955 to 1995)

Improved conditions for mite and mold growth (1955 to 1975)*

Decreased ventilation*

Increased reservoirs for allergen (carpets/sofas) (1935 to 1965)*

II. Changes in hygiene

Clean water

Eradication of helminths and malaria in Europe and United States (1920 to 1940)

Decline in hepatitis A infection (1920 to 1990)

Introduction of broad spectrum antibiotics (approximately 1960)

Increased treatment and control of food to prevent bacterial infection (1900 to 1980)

Immunization to control infectious diseases (1800 to 1990)

III. Lifestyle changes: Secondary to the introduction of sedentary entertainment in homes

Increase in the percentage of homes with television and increase in hours spent watching television (1955 to 1990)

Decline in outdoor "play" (1955 to 1995)

Rise in obesity (1970 to 2000)

Changes in diet following changes in traditional family life (1965 to 2000)

Decreased vitamin D levels secondary to decreased time spent outdoors and decreased intake

* Variable by locale.

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