biphasic allergic reactions…

26 Jan

…are RARE.

via this recent ACEP Now article by Dr. Milne


data from 2 urban ED’s over 5 yrs

~2300 allergic reactions + ~500 anaphylaxis cases

185 returned for 2nd visit

5 (0.18% of ~2800 allergic rxns) were clinically important biphasic reactions

  • 2 were during the initial ED visit
  • 3 were post-discharge (at 28, 35, and 143 hrs s/p)
  • no fatalities



Prolonged observation is likely unnecessary in patients whose symptoms resolve with therapy in the ED. Biphasic reactions are rare and can occur anywhere from 10 minutes up to six days after an initial reaction.”


Food for thought.


References: ACEP Now article; picture



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