Anaphylaxis is a serious, possibly life-threatening allergic reaction. It can have several triggers, most commonly certain medications, foods, and insect bites. However, up to one in five cases of anaphylaxis have an unknown cause.
During anaphylaxis, the body’s immune system overreacts to the trigger allergen and sets in motion a rapid, body-wide allergic reaction. This reaction can lead to many different symptoms that affect several systems in the body. Symptoms may start out as mild but then progress quickly. Anaphylaxis symptoms may begin with a feeling of doom or anxiety before physical symptoms set in.
Healthcare providers generally diagnose anaphylaxis when symptoms involve at least two body systems. Common symptoms of anaphylaxis include:
- Skin symptoms such as hives
- Respiratory symptoms such as trouble breathing
- Cardiovascular symptoms such as low blood pressure (hypotension)
- Gastrointestinal symptoms such as nausea or vomiting
Anaphylaxis typically begins within an hour of exposure to a trigger. Treatment with epinephrine, like an EpiPen, is extremely important to stop the body’s immune response. Without treatment, anaphylaxis can be fatal. Up to half of all cases of anaphylaxis occur at home, so it is crucial to be able to recognize the symptoms and take action immediately.
One criterion healthcare providers use to diagnose anaphylaxis is that skin symptoms are present along with other types of symptoms. Hives (urticaria) are one of the most common and earliest signs of anaphylaxis. Most anaphylactic reactions involve skin symptoms, though some cases do not.
Skin symptoms of anaphylaxis may include:
- Hives: These are raised, red welts on the skin that can vary in size and shape. Hives may appear in one area or spread across large sections of the body.
- Flushing: This is redness of the skin, possibly resembling a sunburn. Flushing usually occurs on the face, neck, or chest.
- Itching: Up to half of adults experiencing anaphylaxis have general itching.
- Swelling: Swelling typically occurs around the face, lips, tongue, or throat. Swelling is particularly dangerous when it affects the airways because this causes trouble breathing.
Respiratory symptoms are among the most dangerous during an anaphylactic reaction. This is because they can quickly lead to life-threatening complications. While these symptoms may begin with a simple runny nose or congestion, they will progress quickly to more serious symptoms. Respiratory symptoms of anaphylaxis can include:
- Trouble breathing (dyspnea): Up to two-thirds of adults with anaphylaxis have shortness of breath or labored breathing. This can lead to dangerously low levels of oxygen in the blood (hypoxemia). If anaphylaxis leads to swelling that causes your airways to close up completely, you may become completely unable to breathe.
- Wheezing or stridor: These are both high-pitched whistling sounds that happen when you breathe. These sounds can mean your airways are narrowing. Wheezing typically sounds more musical than stridor, which may sound like more of a squeak.
- Throat tightness or fullness: A feeling that your throat is closing up or blocked can lead to trouble swallowing or speaking.
- Hoarse voice: Hoarseness can signal that anaphylaxis is affecting your airways.
- Coughing: Persistent coughing that doesn’t improve with typical treatments may be a sign that your airways are obstructed.
Anaphylaxis can affect parts of the cardiovascular system, which includes the heart, arteries, veins, and capillaries. Symptoms related to this system can be life-threatening and may include:
- Chest pain: You may experience chest pain or discomfort during an anaphylactic reaction. It is easy to mistake this symptom for a heart attack.
- Hypotension: Low blood pressure is a serious symptom because it can mean your heart is struggling to pump enough blood to your vital organs. A sudden drop in blood pressure can cause dizziness or fainting.
- Rapid heartbeat: A fast heartbeat may result from your body trying to compensate for the drop in blood pressure.
- Weak pulse: Your pulse may get weaker as anaphylaxis progresses.
A range of gut symptoms may occur when anaphylaxis affects the digestive system. Up to a third of adults with anaphylaxis experience gastrointestinal symptoms. These symptoms may be:
- Nausea and vomiting: Sudden nausea and vomiting can occur as your body reacts to the allergen.
- Diarrhea: Loose or watery stools can be another sign of anaphylaxis.
- Abdominal pain or cramps: You may have severe stomach pain or cramping, possibly along with vomiting or diarrhea.
Sometimes, children have different triggers and symptoms of anaphylaxis than adults. For example, while medications are the most common trigger in adults, foods are the most common trigger in children. Some common food allergens are peanuts, milk, and eggs.
Symptom-related differences in children include:
- Children are more likely than adults to develop hives during anaphylaxis.
- Children are more likely to have respiratory symptoms such as stridor, wheezing, cough, and shortness of breath.
- Children are less likely than adults to have cardiovascular symptoms.
- Healthcare providers are usually more likely to overlook gastrointestinal and respiratory symptoms in children when diagnosing anaphylaxis.
Although they may start out mild, anaphylaxis symptoms can become life-threatening within minutes. If you experience symptoms like throat swelling or difficulty breathing, especially after coming into contact with something you are allergic to, use an EpiPen right away. If you do not have access to an EpiPen, call 911 or ask someone to take you to an emergency room (ER) for treatment. Make sure to seek medical care even after using an EpiPen.
After you have treated the initial symptoms of an anaphylactic reaction, there is a chance symptoms will return up to 72 hours after treatment. This is called a biphasic reaction. A biphasic reaction can happen in up to 20% of people who have recently had anaphylaxis. Tell your healthcare provider right away or go to the ER if you notice any symptoms returning.
Anaphylaxis is a fast-developing allergic reaction that can affect multiple systems in the body. Recognizing anaphylaxis symptoms will help you avoid life-threatening complications. Common symptoms of anaphylaxis include hives, itching, trouble breathing, chest pain, and nausea.
Children may show different signs of anaphylaxis than adults but can also experience skin, respiratory, cardiovascular, and gastrointestinal symptoms. Always seek immediate medical attention if you suspect anaphylaxis, even after using an EpiPen. About half of deaths from anaphylaxis occur within one hour, so quick action is necessary.
