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Anaphylaxis is a life-threatening reaction to an allergen or trigger factor. It can occur within a few seconds or minutes after exposure to something you are allergic to. It is characterized by the release of chemicals and fluids in your body as directed by your immune system. These fluids can accumulate and cause severe symptoms such as narrow airway, shortness of breath, low blood pressure, and weak pulse. Anaphylaxis needs to be treated as a medical emergency. Delay of treatment can prove fatal in most cases. 


Your immune system releases antibodies against possible pathogens and foreign substances whenever it senses a threat. Allergic reactions occur when the immune system gets triggered against substances that are not harmful. In such scenarios, the release of antibodies and other chemicals can cause multiple symptoms that may be mild to moderate in nature. Anaphylaxis occurs when your immune system overreacts to an allergen, leading to the development of severe symptoms.

The triggers of anaphylaxis may vary in different people. Kids are most susceptible to anaphylaxis because their trigger factors are unknown until they are exposed to it. Many people get triggered by certain food allergens such as peanuts, tree nuts, shellfish, wheat, milk, soy, sesame, etc. Apart from food allergies, there can be other trigger factors, which include insect bites, latex, exercise, and certain medications. 

Risk Factors And Epidemiology

The risk of anaphylaxis is difficult to predict as it may develop in any person if they are exposed to a known or unknown allergen. Some studies indicate the risk is higher in individuals with asthma or atopy. These diseases also occur due to a hypersensitive immune system, so it is possible that people with these conditions may react to other allergens as well. Previous history of anaphylaxis also increases the risk in future.

The incidence of anaphylaxis has been found to be higher in boys younger than 15 years and girls older than 15 years. Generally, children and young adolescents are at a higher risk. The occurrence of anaphylaxis in relation to a particular allergen may also vary. For example, the incidence of anaphylaxis due to venom sting is higher among men. 

Signs And Symptoms

Signs and symptoms of anaphylaxis usually develop within a few minutes after being exposed to an allergen. In some instances, the reaction may be delayed and may take half an hour to a few hours to develop. Typical symptoms of anaphylaxis include skin reactions such as hives, itching and redness, reduced blood pressure, weak pulse, rapid heartbeat, constriction of the upper airway, difficulty breathing and swallowing, abdominal pain, nausea/vomiting, dizziness, and fainting. In many people, the throat and tongue may become swollen, which contributes to the constriction of the respiratory tract. If these symptoms persist for a longer duration, they may cause complete airway obstruction, which can prove fatal. 


If you develop symptoms of anaphylaxis, you will need to be taken to an emergency medical ward. Your doctor will require a history of known allergens or whether you had an anaphylactic reaction in the past to food, latex, insect bites, or certain medications. A brief physical examination will reveal skin reactions, weak pulse, crackling or wheezing sounds upon breathing, and low blood pressure. To confirm the diagnosis of anaphylaxis, a blood test can be done to measure the level of tryptase, histamine, and other immune cells. Your doctor may also perform additional blood or skin tests to identify possible allergens. 

Differential Diagnosis

Symptoms of anaphylaxis may resemble those of several other medical conditions. These include carcinoid syndrome, Globus hystericus, hereditary angioedema, pulmonary embolism, pheochromocytoma, scromboid intoxication, vagal reactions, Crohn’s disease, systemic mastocytosis, benign cutaneous flushing, and asthma exacerbation. Differentiation is done on the basis of presenting symptoms at the time, and treatment is started immediately without further delay. 


The first line treatment of anaphylaxis is an injection of epinephrine. If you have a known experience of anaphylaxis in the past, carry self-injectable epinephrine with you always. The potential allergen should be removed from the system if possible. For example, if you see a person who develops anaphylaxis due to A venom sting, place a card below the sting region and slowly push it upwards to expel the sting. Even if you had an initial dose of epinephrine, you or an attendee would still need to call 911 immediately. At a hospital, your airway will be restored, and you will be provided oxygen to stabilize breathing. If your heart or breathing has stopped, immediate CPR will be given to restore their function. Once your airway and circulation have been restored, you will be given additional medications to reduce the symptoms of anaphylaxis.


Intramuscular injection of epinephrine is the primary treatment option. Other medications such as intravenous injection of antihistamine or cortisol can be given to reduce inflammation and swelling. A fast-acting beta-agonist such as Albuterol can also be given to relieve breathing difficulty. 


The prognosis of anaphylaxis may vary depending on the availability of treatment. If prompt treatment is not given, the affected person may die from restricted breathing or reduced heart rate. Anaphylaxis resolves well with treatment. 


Anaphylaxis can be prevented by avoiding all known trigger factors. If you have had allergic reactions to certain food or things in the past, note those down and avoid them as much as possible. Carry an emergency medical kit with you that contains all your necessary medications as prescribed by your doctor. If you are allergic to latex or any drug, mention it to your healthcare provider before they begin the examination. Carefully read labels of food items before consuming anything to look out for possible allergens.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on May 11, 2023. 





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