Anaphylaxis:  Is a severe reaction to released histamine, characterized with rash, hives, wheezing and hypotension.    This reaction can be caused by antigens releasing IgE and Plasma Activating Factor (PAF).   from mast cells or IgG releasing Plasma Activating Factor (PAF) from macrophages.  These reactions can cause death.    

In the US for a population of 280 million, it is estimated that there are 84 thousand cases of anaphylaxis annually with 840 fatalities (Samuel R. Marney Jr MD).  Fatal reactions to skin testing are rare.  Rate of 1 death per 2,000,000 injections for immunotherapy. (Kemp and Lockey  JACI 2002 110, 342)  View PDF Article

Anaphylactoid reaction:   This reaction is similar in type and magnitude to an anaphylactic reaction.  The initiating factors by passes IgE and release histamine directly.    These reactions can cause death.

• Heat, Cold, UV Light

• Exercise

• Opiates - Directly release histamine

• Ethanol

All of these activities can be very dangerous in patients with mastocytosis.  If given opiates during surgery can cause life threatening anaphylactotoid reactions. 

Treatment:  Epinephrine, fluid or Oxygen are key first steps.   If the patient is on B-Blockers administer Glucagon, this will activate the B2 receptor and bypass the blocking agent.  Antihistamines should also be given.   Always give steroids for late phase reactions.  18% to 20% of patients will develop a late phase reaction 4 to 8 hours after the initial reaction.