Wilderness and Rescue Medicine 7th Edition Jeffrey Isaac, PA-C and David E. Johnson, MD

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Wilderness and Rescue Medicine

When the response remains localized to the area of antigen contact, it is called a local allergic reac- tion. The patient experiences localized vasodila- tion. This allows fluid to leak from capillaries into the extracellular space causing localized swelling and itching. Hay fever is an example of a local reaction affecting the mucous membranes of the nose and eyes. These effects explain the familiar symptoms: swollen mucous membranes, itchy eyes, and a runny nose.

Hives tend to appear and disappear from vari- ous areas of the skin surface, sometimes within minutes. Anaphylaxis Anaphylaxis is a severe form of systemic aller- gy that results in critical system problems. Widespread vasodilation and fluid shift into the interstitial space can cause vascular and volume shock, upper airway swelling, vomiting, and diar- rhea. Lower airway constriction results in wheez- ing and respiratory distress. The patient can die within a matter of minutes. Symptoms can progress quickly from an initial complaint of itchy skin and hives with a scratchy or constricted feeling in the throat. Patients often report feeling a sense of impending doom. As the reaction becomes more severe, signs and symp- toms including wheezing, stridor, facial swelling, nausea, vomiting, or diarrhea may develop. There will be weakness and mental status changes with the onset of vascular and volume shock.

General Principles

Mild Allergic Reaction

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Signs and Symptoms: • Generalized hives and itching • Normal mental status • No facial swelling • No tight or scratchy throat • No respiratory distress • No signs of shock

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Low Risk ! High Risk

©2018WMA

A systemic response to an allergen, by contrast, can produce generalized itching and hives all over the body surface. The patient may give a history of a specific allergy, or the history may be completely unrevealing. As long as there is no swelling, no respiratory distress, and no signs of vascular shock, we call this a mild allergic reac- tion. It usually resolves on its own or responds well to treatment with oral antihistamines like diphenhydramine. Often, the patient will give a history of similar symptoms and successful treat- ment with oral medications. This is reassuring for field treatment, but still requires careful monitor- ing because any reaction can be more severe than expected.

General Principles

Anaphylaxis

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Signs and Symptoms: • Itching, hives, or facial swelling • Tight or scratchy throat • Vascular and volume shock • Respiratory distress • Nausea, vomiting, diarrhea • Altered mental status

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Low Risk High Risk

©2018WMA