Grass and ragweed sensitivities were higher in the West, mold allergy more common in the East. Positive tests for indoor allergens were higher in the East than the West, but there were almost no regional differences for peanut, shrimp, egg, dog, cat, rat and mouse sensitivities.
The most common positive tests among the adult group were for dust mites, grass and ragweed, with almost 20 percent of the population showing sensitivity to each. About 12 percent of people over 6 were sensitive to dogs or cats, and among the youngest children, milk and eggs were the most common positive tests. Inhalant allergies like ragweed and grass peaked in the teens and 20s, then decreased later in life.
Race and socioeconomic status also made a difference. Non-Hispanic blacks had the highest sensitivity to all tested allergens except Russian thistle and egg. Sensitivity to cockroaches and shrimp were associated with lower economic status, and dog and cat allergies were more common in higher income groups.
Read more about this at the New York Times on March 6, 2014