A study in the Journal of Allergy & Clinical Immunology says emergency department anaphylaxis cases increased 10% between 1990 and 2000 to a high 150,000 incidents a year.
This number is higher than previous estimates, according to the Mayo Clinic research.
Young people and children under the age of 20 were at highest risk and the most frequent causes of Anaphylaxis were food allergy (33%) and insect sting (18%)

That's pretty scary! I think part of the reason for the rise in food allergies, and all kinds of allergies, is weakened immune systems. I've read that these days, our environment is so clean that our body's immune system never gets to "practice" on very many real germs so it kind of turns on itself, causing allergic reactions to common things like foods.