The prevalence of anaphylaxis in the population has also been very difficult to estimate, in large part because of the fact that a surprising number of individuals never inform their physician about reactions they have experienced. There is also some difficulty with definitions since some mild systemic reactions (e.g. hives without any other manifestations) are not always referred to as anaphylaxis. Epidemiologic surveys have reported systemic reactions to insect stings in 1% of children an 3% of adults. Food allergy is more common in children than in adults. Food-induced anaphylaxis is estimated to occur in 1-3% of children. Drug reactions are also common with anaphylaxis occurring in approximately 1% of adults. Radiocontrast media cause anaphylaxis in 0.1% of procedures performed. Allergen immunotherapy injections cause systemic symptoms in 10-15% of treated patients but anaphylaxis is estimated to occur in 3% of cases. Latex allergy has been increasing in frequency over the past 10 years, with increasing reports of latex anaphylaxis approaching 1% of adults. There have been no accurate reports of the overall prevalence of anaphylaxis, but these various estimates suggest that 5% of adults may have a history of anaphylaxis.