Anaphylaxis: Symptoms, Types, Causes and Treatment

Anaphylaxis is a medical emergency that can be frightening, fast-moving, and life-threatening. Recognizing and acting on the signs and symptoms is crucial for survival. In this article, we'll explore the key aspects of anaphylaxis, including its symptoms, various types, underlying causes, and current best practices for treatment. By understanding the nuances of this severe allergic reaction, you can help ensure timely and effective responses—whether you're a healthcare professional, a patient at risk, or a concerned caregiver.

Symptoms of Anaphylaxis

Anaphylaxis symptoms typically develop suddenly and can escalate rapidly. These symptoms reflect the widespread and systemic nature of the reaction, involving multiple organ systems. Recognizing the signs early is essential for prompt intervention and can make a significant difference in patient outcomes.

Symptom	System	Severity Range	Source(s)
Urticaria	Skin	Mild to severe	1 3 4 5
Angioedema	Skin/Mucosa	Mild to severe	4 5 16
Hypotension	Cardiovascular	Severe	2 1 4 16
Bronchospasm	Respiratory	Moderate-severe	3 5 16
Gastrointestinal symptoms	GI	Mild to moderate	2 4 16
Syncope	Cardiovascular	Severe	1 2 16
Stridor	Respiratory	Severe	2 5 16
No skin symptoms	Any	Severe possible	4 11

Table 1: Key Symptoms of Anaphylaxis

Recognizing Anaphylaxis

Anaphylaxis can present with a wide range of symptoms, often involving more than one organ system. Common early signs include skin reactions like hives (urticaria) and swelling (angioedema), but it's important to note that 10–30% of patients may not show any skin symptoms, which can complicate and delay diagnosis 4 11. In some cases, the first signs may be related to the cardiovascular or respiratory systems.

Systems Commonly Affected

• Skin/Mucosa: Hives, redness, swelling of lips, tongue, or throat.
• Respiratory: Wheezing, shortness of breath, throat tightness, stridor (noisy breathing).
• Cardiovascular: Dizziness, fainting (syncope), low blood pressure (hypotension), rapid or irregular heartbeat.
• Gastrointestinal: Nausea, vomiting, abdominal pain, diarrhea.

Severity and Progression

• Symptoms usually appear within minutes to an hour of exposure to the trigger, but can sometimes be delayed 2 4.
• The most severe reactions can lead to shock, airway obstruction, and cardiac arrest.
• Not every patient will go through all stages; some may rapidly deteriorate without skin warning signs 4 16.

Special Considerations

• Children are more likely to present with respiratory symptoms, while adults may show more cardiovascular involvement 10 16.
• During surgical or medical procedures, typical skin findings may be absent, and cardiovascular collapse may be the primary sign 11.
• Biphasic reactions—where symptoms recur after initial improvement—are possible, especially in severe cases 14.

Types of Anaphylaxis

Anaphylaxis is not a one-size-fits-all reaction. Its types are categorized by underlying mechanisms, triggers, and clinical context. Understanding the distinctions is crucial for both diagnosis and management.

Type	Mechanism/Trigger	Distinguishing Feature	Source(s)
IgE-mediated	Allergen cross-linking	Rapid, classic allergic	3 6 8 16
Non-IgE-mediated	Complement, IgG, direct	Similar symptoms, different pathway	6 8
Idiopathic	Unknown	No clear trigger identified	3 4 8
Occupational	Work-related exposures	Triggered by workplace agents	7
Biphasic	Any (after initial event)	Recurrence after initial resolution	14

Table 2: Main Types of Anaphylaxis

IgE-mediated Anaphylaxis

This is the classic and most well-understood form, where exposure to a specific allergen (such as peanuts, insect venom, or certain medications) causes rapid degranulation of mast cells and basophils via IgE antibodies 3 6. This leads to the release of histamine and other mediators, resulting in the typical cascade of symptoms.

Non-IgE-mediated Anaphylaxis

Some anaphylactic reactions occur without IgE involvement. These can be triggered by:

• IgG antibodies activating complement or other immune cells;
• Direct activation of mast cells by certain drugs;
• Anaphylatoxins such as C3a and C5a 6 8. Symptoms are often indistinguishable from IgE-mediated reactions, but diagnosis and management may differ.

Idiopathic Anaphylaxis

Sometimes, no specific trigger can be identified—even after thorough testing. This is called idiopathic anaphylaxis. It remains a diagnosis of exclusion and may account for a small percentage of cases 3 4.

Occupational Anaphylaxis

This type occurs due to exposures in the workplace, such as latex, laboratory animal proteins, or certain chemicals. It often affects healthcare workers, laboratory staff, and those exposed to insects (e.g., beekeepers) 7.

Biphasic Anaphylaxis

A biphasic reaction refers to the recurrence of symptoms after initial resolution, sometimes several hours after the first wave. This is more likely in severe cases or when epinephrine treatment is delayed or insufficient 14.

Causes of Anaphylaxis

A wide variety of substances can trigger anaphylaxis. The most common causes differ by age, geography, and individual risk factors. Accurate identification of the trigger is vital for prevention and long-term management.

Cause	Population Most Affected	Risk Factor(s)	Source(s)
Foods	Children, young adults	Peanuts, tree nuts, shellfish	1 9 10 12
Medications	Adults, elderly	Antibiotics, NSAIDs, anesthesia	1 5 10 11
Insect stings	All ages, outdoor exposure	Bees, wasps (Hymenoptera)	1 2 4 10
Latex	Healthcare workers, patients	Prior exposure, multiple surgeries	7 11
Exercise	Adolescents, adults	Often food-dependent	9 12
Unknown (idiopathic)	Any	No identifiable trigger	4 8

Table 3: Major Causes of Anaphylaxis

Food-Induced Anaphylaxis

• Foods are the leading cause in children and one of the top causes in adults 1 9 12.
• Common triggers include peanuts, tree nuts, shellfish, fish, and sometimes milk, eggs, or wheat, depending on age and region 9 12.
• Food-induced anaphylaxis is often IgE-mediated, but non-IgE pathways may contribute in some cases 12.
• Symptoms can be more severe if food ingestion is combined with exercise (food-dependent exercise-induced anaphylaxis) 9 12.

Medication-Induced Anaphylaxis

• Medications are a leading cause in adults, especially older adults 1 5 10.
• Common drugs: antibiotics (penicillins, cephalosporins), NSAIDs, and anesthesia agents 1 11.
• During surgery, muscle relaxants and latex are major culprits 11.
• Drug-induced anaphylaxis can be IgE-mediated or occur through direct mast cell activation 5 6.

Insect Venom

• Stings from bees, wasps, and hornets (Hymenoptera) are a major cause, especially in outdoor workers or those with known allergies 1 2 4 10.
• Reactions can be severe and rapid, often requiring immediate treatment.

Latex

• Latex allergy is a significant occupational hazard for healthcare workers and patients with repeated medical procedures 7 11.
• Reactions can be severe and may occur during surgery or dental work.

Other Triggers and Idiopathic Cases

• Exercise, sometimes in combination with specific foods, can trigger anaphylaxis 9 12.
• Some individuals experience anaphylaxis without any identifiable cause (idiopathic) 4 8.
• Occupational exposures, such as laboratory animal proteins or chemicals, are increasingly recognized 7.

Risk Factors for Severe Reactions

• Older age, male sex, and drug-induced anaphylaxis are associated with increased severity 1.
• Asthma, especially if poorly controlled, increases risk of fatal reactions 16.
• Delay in administration of epinephrine is a major risk for worse outcomes 3 14 16.

Treatment of Anaphylaxis

Prompt, decisive action is vital when anaphylaxis is suspected. The main goal is to halt the reaction, support vital functions, and prevent recurrence. Guidelines are clear: epinephrine is the cornerstone of therapy.

Treatment	Purpose	Key Point	Source(s)
Epinephrine	First-line, reverses symptoms	Intramuscular, ASAP	3 13 14 15 16 17
Airway support	Maintain oxygenation	May require intubation	13 16
Antihistamines	Symptom relief	Not first-line or lifesaving	14 16
Corticosteroids	Prevent protracted/biphasic	Limited evidence for prevention	14 16
Observation	Monitor for recurrence	Especially after severe cases	14 16
Education	Prevent recurrence	Epinephrine auto-injector, action plan	3 13 14 15 16

Table 4: Emergency and Long-term Treatment of Anaphylaxis

Immediate Management

• Remove the trigger: If possible, eliminate the source (e.g., stop the drug, remove the stinger) 16.
• Epinephrine (adrenaline): Administer intramuscularly into the mid-outer thigh as soon as anaphylaxis is suspected. There are no absolute contraindications 3 13 14 15 16.
  • Dose: 0.01 mg/kg (maximum 0.5 mg per dose), repeat every 5–10 minutes if needed 16.
  • Delays in epinephrine use are associated with worse outcomes and increased fatalities 3 14 16.
• Positioning: Lay the patient supine with legs elevated unless breathing is difficult; do not sit or stand suddenly 16.
• Airway, Breathing, Circulation (ABCDE): Assess and support as needed. Oxygen, intravenous fluids, and advanced airway management may be necessary 13 16.

Adjunctive Therapies

• Antihistamines: Can relieve cutaneous symptoms but are not life-saving or sufficient as sole therapy 14 16.
• Corticosteroids: May help prevent protracted or biphasic reactions; evidence for efficacy is limited 14 16.
• Other measures: In refractory cases, inhaled beta-agonists for bronchospasm, vasopressors for persistent hypotension 16.

Observation and Follow-up

• Monitor for recurrence of symptoms, especially in severe or biphasic cases 14 16.
• Minimum observation of 4–6 hours, longer if risk factors present 14.

Education, Prevention, and Long-term Care

• All patients should be referred to an allergy specialist for trigger identification, risk assessment, and preventive planning 3 14 15 16.
• Prescribe and train patients in the use of epinephrine auto-injectors; ensure they have more than one device and understand their emergency action plan 3 13 14 15 16.
• Emphasize strict avoidance of known triggers and encourage wearing medical identification 9 12 14.

Conclusion

Anaphylaxis is a rapidly evolving, potentially fatal allergic reaction that requires immediate recognition and intervention. Understanding its symptoms, types, triggers, and treatment protocols is essential for both patients and healthcare providers.

Key Takeaways:

• Symptoms: Can involve skin, respiratory, cardiovascular, and gastrointestinal systems; absence of skin findings does not rule out anaphylaxis.
• Types: Include classic IgE-mediated, non-IgE-mediated, idiopathic, and occupational forms, with possible biphasic patterns.
• Causes: Most often triggered by foods, medications, insect stings, or latex; risk factors for severe reactions include older age, drug triggers, asthma, and delayed treatment.
• Treatment: Immediate intramuscular epinephrine is the first and most critical step; adjuncts may help, but do not replace epinephrine. Education and prevention are vital for long-term management.

By increasing awareness, ensuring access to epinephrine, and promoting comprehensive patient education, we can improve outcomes for those at risk and reduce the burden of this life-threatening emergency.