In an emergency situation, your doctor will quickly diagnose anaphylaxis according to visible symptoms and immediately treat you.
This is because time is of the essence, and it would be a risk to your life to try to confirm an anaphylactic reaction with lab tests before administering treatment.
A rapid diagnosis of anaphylaxis is made on the basis of one of two scenarios.
If it is unknown whether you were exposed to an allergen and you have rapidly developing hives or other skin symptoms, a provider will look for at least one of the following:
- Respiratory symptoms such as shortness of breath, wheezing, low blood oxygen levels, or persistent cough or throat-clearing
- Hypotension, or low blood pressure
- Symptoms that indicate your organ function is impaired, for example your muscles are soft and flabby, you’re fainting, or incontinent
If it is known or likely that you were exposed to an allergen, your provider will look for at least two of the following:
- Symptoms affecting your skin such as rash, hives, itchiness, reddening of the skin, or swelling of the face, lips, tongue, or uvula
- Respiratory symptoms such as shortness of breath, wheezing, low blood oxygen levels, or persistent cough or throat-clearing
- Hypotension
- Gastrointestinal symptoms such as vomiting or painful cramps
If your symptoms are relatively mild and 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 emergency situation — the priority is rapid treatment.
When possible, 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 the airway
- Pulmonary embolism (a blood clot in the lungs)
- Autonomic epilepsy or seizure disorder
- Stroke
- Drug overdose
- Monosodium glutamate or sulfite ingestion
- Reaction to vancomycin infusion
- Leukemia
- Flushing syndromes
- Vocal cord dysfunction
- Panic attack
The list of possible conditions that share the symptoms of anaphylaxis would be in the hundreds, says Torbati. But, “most of the time it’s not a difficult diagnosis. If the history is there, like an insect bite or an exposure to a known allergen, diagnosis becomes simple.”
After emergency care for anaphylaxis, it’s a good idea to follow up with an allergist who can evaluate your risk of anaphylaxis generally and help figure out whether any previous symptoms were related to the condition. Your doctor will investigate all potential causes of your symptoms. This may involve allergy tests as well as tests for other health conditions.
To determine what to test for, your doctor will likely ask you about the symptoms and situations involved in past allergic reactions, even if your response didn’t involve anaphylaxis.
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 ensure you have a plan to avoid potential triggers and treat anaphylaxis if it occurs.
Additional reporting by Nina Wasserman.
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