Anaphylaxis is a severe allergic reaction that tends to affect multiple areas of your body at once.
It can be caused by a number of different allergens, or triggers, including foods, medications, latex, and insect venom, among others.
In a typical allergic reaction, bothersome symptoms occur in one area of your body, such as your skin.
An anaphylactic reaction tends to involve several different symptoms in different locations, all of them starting more or less at the same time.
It’s essential to recognize the symptoms of anaphylaxis quickly, so that you can seek immediate treatment, as the reaction can lead to respiratory distress and death.
If you’re having your first anaphylactic reaction, you may not recognize what’s happening at the onset of symptoms. But as soon as it’s clear that you’re having a serious reaction, you should seek emergency medical treatment.
Symptoms of anaphylaxis typically develop quickly after you’re exposed to the allergen that causes them. If you know that you’ve been exposed to an allergen, this can help make clear that your symptoms are part of an allergic reaction.
Your doctor will diagnose anaphylaxis on the basis of your symptoms, and possibly blood or urine tests. (1,2,3)
Signs of Anaphylaxis
Anaphylaxis symptoms typically begin within 5 to 30 minutes after you come into contact with the allergen that causes them, according to the American Academy of Allergy, Asthma & Immunology. (1)
Less commonly, it can take an hour or longer for anaphylaxis to develop.
The first sign of anaphylaxis is often a creeping sense of unease. This can be a sign to someone with a history of anaphylaxis that a reaction is coming.
Symptoms of anaphylaxis typically affect more than one part of your body. They may include:
- Red rash with hives or welts (usually itchy)
- Flushed or pale skin
- Swollen throat
- Swelling of your face, eyes, tongue, or other areas of your body
- Wheezing or coughing
- Chest tightness or trouble breathing
- Hoarse voice
- Nasal congestion
- Trouble swallowing
- Nausea or vomiting
- Stomach cramps
- Weak or rapid pulse
- Dizziness or fainting
- Heart palpitations
- Anxiety or sense of impending doom
- Loss of consciousness (1,2,4)
It’s possible to have a severe anaphylactic reaction without any single one of these symptoms. This means that while there are common patterns, there’s no one “telltale sign” of anaphylaxis. (1)
Anaphylaxis can progress very quickly, with some people collapsing, no longer breathing, having seizures, or losing consciousness within one to two minutes. In these severe cases, the reaction can be fatal unless emergency care is immediately available. (3)
Anaphylaxis can lead to shock, a biological reaction involving dangerously low blood pressure and a rapid, weak pulse.
Shock can also cause confusion and cold, sweaty skin.
Not all cases of anaphylaxis lead to shock, but those that do are especially dangerous. It’s important, when possible, to treat your anaphylaxis before you go into shock.
Regardless of whether you experience shock, an anaphylactic reaction requires immediate attention and emergency medical care. (3,4)
In an emergency situation, your doctor will most likely quickly diagnose anaphylaxis according to visible symptoms and proceed immediately to treating you.
This is done because time is of the essence, and confirming an anaphylactic reaction with lab tests before administering treatment would mean risking your life.
A rapid diagnosis of anaphylaxis will be based on the following factors:
Symptoms of Shock These may include low blood pressure, sweaty skin, confusion, or a weak, rapid pulse.
Respiratory Symptoms These include difficulty breathing, wheezing, and gasping when breathing in.
Two or More Other Factors Other symptoms used to confirm a diagnosis may include swelling, hives and itchiness, nausea or vomiting, or other digestive symptoms.
If your symptoms are relatively mild or don’t clearly indicate anaphylaxis, your doctor may order one or more blood or urine tests. These tests measure levels of certain chemicals that your immune system produces during an allergic reaction.
But these tests are usually unnecessary in an urgent or emergency situation. (3)
Your doctor may want to order tests, or investigate other conditions that may be responsible for your symptoms if you have some signs of anaphylaxis but not enough to make a rapid diagnosis.
It’s important to make sure your symptoms aren’t caused by another condition if they don’t clearly indicate anaphylaxis. That’s because another condition may also require urgent treatment, and could be made worse by anaphylaxis treatment.
Conditions that could be mistaken for anaphylaxis include:
- Generalized hives or swelling
- Shock caused by cardiovascular issues (cardiogenic or hypovolemic shock)
- Fainting (due to nonallergic factors)
- Certain endocrine problems (carcinoid syndrome or pheochromocytoma)
- Foreign object stuck in airway
- Pulmonary embolism (a blood clot in the lungs)
- Autonomic epilepsy or seizure disorder
- Drug overdose
- Monosodium glutamate or sulfite ingestion
- Reaction to vancomycin infusion
- Flushing syndromes
- Vocal cord dysfunction
- Panic attack (5)
It’s a good idea to follow up an episode of anaphylaxis, after receiving emergency care, with a visit to a doctor who specializes in allergies.
At this appointment, your doctor can evaluate your risk for anaphylaxis and help figure out whether any previous symptoms were related to the condition.
Your doctor will conduct an investigation of all potential causes of your symptoms. This may involve allergy tests as well as tests for other health conditions.
To help determine what to test for, your doctor will most likely ask you about the symptoms and situations involved in past allergic reactions, even if your response didn’t involve anaphylaxis. (1)
If you or your child has a severe allergy attack or has experienced signs of anaphylaxis in the past — even if the event seemed isolated — it’s a good idea to see an allergist to make sure you have a plan to avoid exposure to potential triggers and treat anaphylaxis if it occurs. (2)
For example, your doctor may prescribe an epinephrine autoinjector, a small and easy-to-carry device that you can use to inject a dose of medicine in case of an anaphylactic reaction.