What are the causes of one to be allergic to wasp or bee stings?

Protein in venom. A person who is allergic to stinging insects has developed an allergy to a protein in the insect venom. These proteins have been well described and include mellitin, hyaluronidase, phospholipase, etc. Why this happens to some people is unclear. Thankfully treatment with venom allergy injections is very successful.