A study published in the July 2007 issue of the Journal of Allergy and Clinical Immunology suggests strong variation in the occurence of anaphlyaxis between northern and southern U.S. states, reports the American Academy of Allergy, Asthma & Immunology.

Southern states have the fewest number of Epipen prescriptions per 100 people, while New England states have the most. The highest number of EpiPen prescriptions per 1000 people is in Massachusetts, and the lowest number is in Hawaii.

Some investigators hypothesize that since southern states have more year-round sunlight (which produces Vitamin D in the skin), the southern states may have a lower incidence of allergic disease because people there have higher Vitamin D levels.