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Anaphylaxis is a severe and potentially life-threatening allergic reaction that occurs rapidly in four stages after exposure to an allergen. This reaction occurs due to an overreactive immune response to the allergen, which the body mistakenly perceives as harmful. These can be foods, medications, insect stings, latex, or something else.
The immune system releases a flood of chemicals that can cause a range of body-wide symptoms. Symptoms include difficulty breathing, swelling of the face and throat, rapid heartbeat, low blood pressure, gastrointestinal (GI) distress, and skin reactions like hives or itching.
Anaphylaxis is a medical emergency that requires immediate epinephrine (adrenaline) treatment. Epinephrine counteracts the allergic reaction and stabilizes symptoms. Some people may require additional treatments. If left untreated, anaphylaxis can progress rapidly, leading to complications or death.
About one in 50 Americans have experienced anaphylaxis.3 Understanding anaphylaxis is crucial for people at risk and their families to recognize the signs and symptoms. Appropriate management can save lives.
Anaphylaxis Symptoms
Anaphylaxis symptoms develop suddenly and quickly progress. Specific symptoms vary from person to person, but anaphylaxis can affect the entire body.4
Respiratory Symptoms
Breathing-related anaphylaxis symptoms can include:
Chest tightness
Difficulty breathing
Shortness of breath (dyspnea)
The sensation of a swollen throat
Wheezing
Skin Symptoms
Anaphylaxis can affect the skin and may cause:
Flushed appearance and a warm sensation throughout the body
Hives, or raised red bumps on the skin
Itchiness
Gastrointestinal (GI) Symptoms
Anaphylaxis symptoms that affect the digestive system can include:4
Abdominal pain
Diarrhea
Nausea
Vomiting
Cardiovascular Symptoms
Anaphylaxis symptoms related to the heart can include:5
Dizziness or fainting (syncope)
Low blood pressure (hypotension)
Rapid heartbeat (tachycardia)
Other Symptoms
Anaphylaxis symptoms may also include:5
Anxiety or an impending sense of doom
Slurred speech
Swelling of the face, lips, tongue, or throat
Causes
Anaphylaxis occurs when the immune system overreacts after exposure to an allergen. The immune system sees the allergen as a threat and releases a flood of chemicals, including histamine, when some people with allergies come into contact with a trigger. These chemicals lead to the characteristic anaphylaxis symptoms.6
Allergens known to cause anaphylaxis include:
Certain foods, such as tree nuts, shellfish, peanuts, milk, and eggs
High-intensity exercise, especially when paired with temperature or seasonal changes or after eating certain foods
Insect stings and bites
Latex
Medications, such as penicillin and non-steroidal anti-inflammatory drugs (NSAIDs)
Risk Factors
Not everyone with allergies will go into anaphylaxis when exposed to an allergen. Several risk factors can increase the likelihood of anaphylaxis, including:
A personal history of asthma (especially if not well-controlled, which puts you at a higher risk of having a severe reaction)
Heart disease
Past anaphylactic reaction(s)
Severe or life-threatening allergies
Diagnosis
Anaphylaxis is primarily a clinical diagnosis. Healthcare providers evaluate symptoms and medical history to make a diagnosis rather than relying solely on diagnostic tests.8 They may use tests after treatment to confirm the diagnosis, see what caused the anaphylactic response (if unknown), and develop a comprehensive management plan to prevent future episodes.
Diagnostic tests can include:
Allergy testing: Skin prick allergy testing involves placing a small number of substances (allergens) on the skin and then scratching the skin. This allows the substance to go under the skin’s surface. Your skin may become red, swollen, and itchy within minutes if you are allergic to a substance. These symptoms indicate that the immune system has produced allergen-specific IgE antibodies.
Blood tests: A blood sample taken during or shortly after anaphylaxis allows healthcare providers to measure levels of an enzyme called tryptase. This enzyme is released by immune cells during an allergic reaction.