Anaphylaxis is a serious allergic reaction that develops rapidly and can cause death. Some patients experience anaphylaxis is association with exercise, a disorder called exercise-induced anaphylaxis. A subset of patients with unexplained anaphylaxis, especially those with hypotension during the anaphylactic episodes, have been shown to have abnormal, clonal populations of a certain cell type, mast cells, in the bone marrow. This has been described in at least one patient with exercise-induced anaphylaxis. The investigators would like review the findings in a group of patients with exercise-induced anaphylaxis who have undergone evaluation for the presence of abnormal, clonal mast cells.

Inclusion Criteria:

• Anaphylaxis in association with exercise on at least two occasions
• During anaphylactic reaction, the subject must have experienced one or more of the following: flushing, hypotension, lack of urticaria

Exclusion Criteria:

• Pregnancy

Ten adults of either sex