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Anaphylaxis - Causes, Symptoms, Diagnosis, and Treatment

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Our body’s immune system can overreact to harmless substances and cause anaphylaxis. These life-threatening allergies require immediate emergency care.

Medically reviewed by

Dr. Kaushal Bhavsar

Published At February 1, 2023
Reviewed AtDecember 5, 2023


Allergies are caused when our body overreacts to a harmless substance. Anaphylaxis is a severe form of allergy that is life-threatening. This allergic reaction is multi-systemic and is triggered by common harmless substances, such as foods, latex, medications, and insect stings. The anaphylaxis symptoms can occur within minutes or hours after exposure to the allergen (substance triggering the allergic reaction). Anaphylaxis can quickly affect the patient’s breathing, blood pressure, and heart and requires emergency care. Without quick medical intervention, these can be fatal.

What Are the Common Causes of Anaphylaxis?

Anaphylactic episodes may be caused by harmless common allergens, including the following;

  1. Food: Common foods such as fish, peanuts, tree nuts (such as cashews, almonds, pecans, and walnuts), milk, shellfish, and eggs are known to cause anaphylaxis.

  2. Insect Bites and Stings: Stings of hornets, wasps, fire ants, and other insects can cause anaphylaxis episodes.

  3. Medications: Drugs such as Penicillin are known to cause severe anaphylactic reactions. Common drugs such as pain relievers (such as Ibuprofen and Aspirin) and antibiotics can also trigger anaphylaxis. In addition, dyes used in medical scans and general anesthetics (medicines that put you to sleep during surgery or other invasive procedures) can cause anaphylaxis episodes.

  4. Other Allergens: Repeated exposure to allergens like latex increases the risk of anaphylactic episodes. People with previous mild episodes are at risk of developing severe allergic attacks. In rare cases, these can also occur without any triggers.

What Are the Symptoms of Anaphylaxis?

When a person comes in contact with the allergy-causing substance, the symptoms can start within a few minutes (five to 30 minutes) or may become noticeable later (after an hour or so). Anaphylaxis affects more than one body part, including the respiratory system and the heart. In severe cases, it can lead to the inability to breathe, shock, and heart failure. In addition, anaphylaxis can cause the following symptoms and signs:

  1. Swelling of the tongue.

  2. Swelling of the throat and airway.

  3. Breathing difficulty (caused by swelling of the throat and narrowing of the airway).

  4. Swelling of the face.

  5. Wheezing.

  6. Coughing.

  7. Difficulty in swallowing.

  8. Slurred speech.

  9. Confusion.

  10. Anxiety.

  11. Unusual breathing sounds.

  12. Itchiness and redness of the area affected, such as eyelids, lips, and skin.

  13. Hives and skin eruptions.

  14. Fluttering heart (palpitations).

  15. Nausea and vomiting.

  16. Stomach cramps and diarrhea.

  17. Skin starts to appear blue, especially on the nail bed and lips.

  18. Fast and weak pulse.

  19. Drop in blood pressure.

  20. Dizziness or fainting.

  21. Unconsciousness.

How Is the Risk of Anaphylaxis Diagnosed?

It is essential to visit an allergy clinic and consult an allergy specialist to identify the triggers for anaphylaxis. The doctor usually gets a detailed history, including the specific details of all the past allergies, thoroughly investigates all the potential causes, and diagnoses the risk of anaphylaxis. Then, various tests, including the following, are done to identify the cause of anaphylaxis:

  1. A Patch Test or Skin Prick Test: A small amount of the suspected allergen is put on the skin, and the reaction to it is checked.

  2. Blood Tests: Special blood tests are done to check for the allergens causing the symptoms.

  3. A Special Diet: The doctor recommends avoiding certain foods that can be possible triggers.

What to Do if a Person Has a Severe Anaphylactic Episode?

The steps to follow in case of anaphylaxis include the following:

  1. First, call for emergency medical help immediately and inform the emergency personnel that the patient might have an anaphylactic reaction.

  2. If the patient becomes unconscious, position the patient to lie flat and keep their feet elevated.

  3. Administer self-injectable emergency drug Epinephrine if trained (examples include Twinject and Epipen). The emergency drugs usually are carried by the patient at risk for anaphylaxis. The person providing first aid can use the prescribed auto-injector in case of severe anaphylaxis.

  4. Check for medical bracelets or tags to identify the triggers of the anaphylactic episode.

  5. Whenever possible, remove the triggers, such as stingers stuck to the skin.

  6. If the patient has trouble breathing, the patient can be made to sit up or be positioned comfortably till emergency help arrives.

  7. Pregnant women should be positioned to lie on their left side. Proper positioning of the patient is essential to prevent complications.

How Are Anaphylactic Emergencies Treated?

  • The patient is immediately taken to the nearest emergency department in case of anaphylaxis. Prompt evaluation of the patient’s condition, monitoring, and treatment initiation can help save lives.

  • Immediate cardiopulmonary resuscitation is performed if the patient is having breathing difficulty, shock, or heart failure due to anaphylaxis. Oxygen supplementation through masks and intubation (tubes inserted to help with breathing) is done whenever necessary.

  • Fluid resuscitation is initiated if the blood pressure drops. Intravenous access is obtained to give the fluids directly into the blood. Blood tests are performed to confirm anaphylaxis and identify triggers if unknown.

  • Besides Epinephrine, other medications such as antihistamines (anti-allergy drugs) and steroids are given to calm the patient’s overactive immune system and relieve symptoms. The systemic complications due to anaphylaxis are assessed and managed accordingly.

  • It is usual to keep the patient under observation in the hospital for six to 12 hours till the symptoms subside. During discharge, the patient is usually prescribed medications for a few days to prevent the symptoms.

How to Prevent Anaphylaxis?

  1. It is vital to identify the possible triggers of the allergic attack.

  2. If a patient has had anaphylactic reactions, a visit to an expert doctor (immunologist or an allergist) is essential. The consultation will help identify the triggers and help develop an emergency plan to keep the patient safe.

  3. Avoid exposure to allergens that can cause anaphylaxis. If you have a known food or medication allergy, do not consume it.

  4. Caregivers, friends, and family members should be informed about the allergy-causing agents and how to deal with an anaphylactic episode.

  5. Always carry the prescribed auto-injectors (Epinephrine) to use in case of an allergic response.


Our body’s immune system can overreact to harmless substances and cause anaphylaxis. For example, food such as fish, nuts, or milk, insect bites, and certain medications can trigger anaphylactic episodes. Anaphylaxis causes breathing difficulty, lowers blood pressure, and can lead to shock and heart failure. It is life-threatening and requires immediate medical attention. Patients with a known risk of anaphylaxis should always carry prescribed self-injectable Epinephrine with them for use during an emergency. One must identify and avoid the triggering allergens to prevent future anaphylactic attacks.

Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)


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