Exercise induced anaphylaxis

Rare but well recognized allergic condition, about half related to a food trigger.

Anaphylaxis can occur with any degree of exercise, does not need to be extreme, but typically follows submaximal exercise pretty quickly.  Deaths are fortunately rare.

Possible mechanisms:

  • Exercise induced increase in gastric permeability
  • increased tissue transglutaminase activity in gut
  • Exercise induced blood flow redistribution
  • Mast cell heterogeneity
  • Basophil trigger by increased plasma osmolality
  • Mast cell trigger by acidosis

All sound plausible but little evidence!

Co-factors play a role in many cases eg alcohol (but unpredictable), NSAIDs (85% will have reduced threshold, and severity increases too), infection, heat/cold – some evidence too for menstruation, anti-acids, stress, sleep deprivation (as in anaphylaxis).  Co-factors also multiply risk of reaction.

Food triggers

Mostly wheat, including hidden sources eg soap, shampoo, cream.

Diagnosis

SPT useful, also IgE omega-5-gliadin.  But gold standard is provocation test (and still only 70% sensitive).  No uniform protocol – use same as for exercise induced bronchoconstriction? Do 1 hour after meal with suspected trigger.

Management

Prescribe adrenaline auto-injector.  Avoid exercise 4-6 hours after food intake.  Discuss unplanned exercise!

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