Anaphylaxis

Anaphylaxis, or anaphylactic reaction, is the most severe allergic manifestation that exists, as it can be fatal. It is a systemic hypersensitivity reaction, meaning that it affects the entire body and develops rapidly.

Depending on the severity of the clinical presentation, anaphylaxis is classified into four grades:

• Mild anaphylaxis: symptoms appear in the skin, eyes, nose, gastrointestinal tract, or as isolated wheezing in the bronchi.
• Moderate anaphylaxis: more intense respiratory symptoms occur, with mild respiratory distress.
• Severe anaphylaxis: severe respiratory symptoms develop, accompanied by cyanosis, loss of consciousness, and decreased oxygen saturation.
• Anaphylactic shock: sudden drop in blood pressure, cardiac rhythm disturbances, laryngeal swelling, inability to breathe, and cardiac arrest.

In recent years, cases of anaphylaxis in infants and children have increased considerably. Factors thought to contribute include the overall increase in food allergies, changes in lifestyle habits, and improved specialist awareness and recognition of the condition.

Allergy-associated anaphylaxis requires immediate medical intervention, as it can progress within minutes and endanger the patient's life.

Symptoms

Symptoms of anaphylaxis usually appear suddenly, generally between 5 and 30 minutes after exposure to the allergen, although they may occasionally take longer to develop. These signs typically involve several organs and systems simultaneously. The most characteristic symptoms are:

• Skin and mucous membranes:
  • Redness.
  • Itching.
  • Urticaria (large hives, swelling, and intense itching).
  • Wheals.
  • Angioedema (swelling of the eyelids, tongue, lips, or uvula).
  • In the most severe cases:
    • Itching and redness of the palms of the hands and soles of the feet.
    • Cyanosis (bluish discoloration of the skin).
• Eyes and nose:
  • Tearing.
  • Red eyes.
  • Ocular or nasal itching.
  • Eyelid edema (swelling of the eyelids due to fluid accumulation).
  • Sneezing.
  • Runny nose.
  • Nasal congestion.
• Larynx:
  • Dry cough.
  • Aphonia.
  • Dysarthria (difficulty speaking).
  • Dysphagia (difficulty swallowing).
  • Stridor (high-pitched sound when inhaling).
• Bronchi:
  • Cough.
  • Wheezing (a high-pitched whistling sound during breathing).
  • Chest pain.
  • Shortness of breath.
  • Bronchospasm (complete closure of the bronchi, resulting in total loss of respiratory capacity).
• Digestive system:
  • Vomiting.
  • Abdominal cramps.
  • Diarrhea.
  • Abdominal pain.
• Cardiovascular system:
  • Hypotension.
  • Generalized malaise.
  • Dizziness.
  • Blurred vision.
  • Loss of consciousness.
  • Seizures.
  • Hypoxemia (low oxygen levels in the blood).
• Nervous system:
  • Distress.
  • Sense of impending doom.
  • Anxiety.
  • Confusion.

Although some symptoms are not serious when considered individually, the danger of anaphylaxis lies in their ability to worsen suddenly. Therefore, any allergic reaction should be considered potentially serious.

Causes

Anaphylaxis occurs when the immune system overreacts to a substance that is normally harmless (an allergen). The most common causes of this allergic reaction are:

• Food-induced anaphylaxis: one of the most common forms, especially in children. Severe food allergy reactions are usually triggered by tree nuts, shellfish, milk, eggs, or fish.
• Insect sting anaphylaxis: allergic reactions to bee or wasp venom are very common.
• Drug-induced anaphylaxis: although any medication may cause it, the most frequent triggers are antibiotics and nonsteroidal anti-inflammatory drugs (NSAIDs).
• Latex-induced anaphylaxis: commonly occurs as an abnormal reaction to the use of gloves or handling balloons.
• Exercise-induced anaphylaxis: occurs when exercise is performed after consuming a specific food; therefore, the possibility of an underlying food hypersensitivity is currently being investigated.
• Catamenial anaphylaxis: a rare type in which food allergy symptoms worsen due to the influence of progesterone. Consequently, some women experience more severe allergic reactions in the days preceding or during menstruation.
• Idiopathic anaphylaxis: anaphylaxis in which no cause has been identified.

Risk Factors

The risk of experiencing an anaphylactic reaction increases under the following conditions:

• History of anaphylaxis: having previously experienced an allergic reaction significantly increases the likelihood of another episode.
• Identified allergies.
• Asthma, especially if poorly controlled.
• Mastocytosis: a rare disease characterized by an increased number of mast cells, a type of white blood cell that plays a key role in allergic reactions.

Complications

Biphasic anaphylaxis is one of the most relevant complications. It consists of the recurrence of symptoms several hours after the initial reaction has been controlled, without renewed exposure to the allergen.

Anaphylactic shock, meanwhile, is the most serious complication of anaphylaxis. In these cases, respiratory or cardiac failure occurs and may lead to death within minutes.

Which doctor treats anaphylaxis?

An acute episode of anaphylaxis is a medical emergency that must be treated in an Emergency department department. Once the patient has been stabilized, specialists in Allergology become involved to identify the cause and provide subsequent follow-up.

Cases of mild allergic reactions may be managed within the specialties of Family and community medicine or Pediatrics.