Signs and Symptoms Anaphylaxis
Anaphylaxis is an acute, potentially fatal, multiorgan system reaction caused by the release of chemical mediators from mast cells and basophils. The classic form involves prior sensitization to an allergen with later reexposure, producing symptoms via an immunologic mechanism.
Anaphylaxis most commonly affects the cutaneous, respiratory, cardiovascular, and gastrointestinal systems. The skin or mucous membranes are involved in 80-90% of cases. A majority of adult patients have some combination of urticaria, erythema, pruritus, or angioedema. However, for poorly understood reasons, children may present more commonly with respiratory symptoms followed by cutaneous symptoms. It is also important to note that some of the most severe cases of anaphylaxis present in the absence of skin findings.
Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death. It typically causes more than one of the following: an itchy rash, throat or tongue swelling, shortness of breath, vomiting, lightheadedness, and low blood pressure. These symptoms typically come on over minutes to hours. Common causes include insect bites and stings, foods, and medications. Other causes include latex exposure and exercise. Additionally cases may occur without an obvious reason. The mechanism involves the release of mediators from certain types of white blood cells triggered by either immunologic or non-immunologic mechanisms. Diagnosis is based on the presenting symptoms and signs after exposure to a potential allergen.
The primary treatment of anaphylaxis is epinephrine injection into a muscle, intravenous fluids, and positioning the person flat. Additional doses of epinephrine may be required. Other measures, such as antihistamines and steroids, are complementary. Carrying an epinephrine autoinjector and identification regarding the condition is recommended in people with a history of anaphylaxis. Worldwide, 0.05–2% of the population is estimated to experience anaphylaxis at some point in life. Rates appear to be increasing. It occurs most often in young people and females. Of people who go to a hospital with anaphylaxis in the United States about 0.3% die.
Signs and Symptoms
Anaphylaxis typically presents many different symptoms over minutes or hours with an average onset of 5 to 30 minutes if exposure is intravenous and 2 hours if from eating food. The most common areas affected include: skin (80–90%), respiratory (70%), gastrointestinal (30–45%), heart and vasculature (10–45%), and central nervous system (10–15%) with usually two or more being involved.
Initially, patients often experience pruritus and flushing. Other symptoms can evolve rapidly, such as the following:
- Dermatologic/ocular: Flushing, urticaria, angioedema, cutaneous and/or conjunctival injection or pruritus, warmth, and swelling. Symptoms typically include generalized hives, itchiness, flushing, or swelling (angioedema) of the afflicted tissues. Those with angioedema may describe a burning sensation of the skin rather than itchiness. Swelling of the tongue or throat occurs in up to about 20% of cases. Other features may include a runny nose and swelling of the conjunctiva. The skin may also be blue tinged because of lack of oxygen.
- Respiratory: Nasal congestion, coryza, rhinorrhea, sneezing, throat tightness, wheezing, shortness of breath, cough, hoarseness, dyspnea. Respiratory symptoms and signs that may be present include shortness of breath, wheezes, or stridor. The wheezing is typically caused by spasms of the bronchial muscles while stridor is related to upper airway obstruction secondary to swelling. Hoarseness, pain with swallowing, or a cough may also occur
- Cardiovascular: Dizziness, weakness, syncope, chest pain, palpitations. Coronary artery spasm may occur with subsequent myocardial infarction, dysrhythmia, or cardiac arrest. Those with underlying coronary disease are at greater risk of cardiac effects from anaphylaxis. The coronary spasm is related to the presence of histamine-releasing cells in the heart. While a fast heart rate caused by low blood pressure is more common, a Bezold–Jarisch reflex has been described in 10% of cases where a slow heart rate is associated with low blood pressure. A drop in blood pressure or shock (either distributive or cardiogenic) may cause the feeling of lightheadedness or loss of consciousness. Rarely very low blood pressure may be the only sign of anaphylaxis
- Gastrointestinal: Dysphagia, nausea, vomiting, diarrhea, bloating, cramps
- Neurologic: Headache, dizziness, blurred vision, and seizure (very rare and often associated with hypotension)
- Other: Metallic taste, feeling of impending doom