FIRST AID  
ANAPHYLAXIS

Symptoms of Anaphylaxis

By Rod Brouhard, EMT-P 
Updated on May 12, 2022
 Medically reviewed by Michael Menna, DO

Anaphylaxis is a sudden and severe allergic reaction that involves more than one body system. It is a life-threatening medical emergency.1 You will often have skin reactions and shortness of breath, which can develop into anaphylactic shock with a drop in blood pressure. Learn how to identify an anaphylactic reaction so you can seek immediate medical care.

anaphylaxis symptoms
Illustration by Verywell

Frequent Symptoms 

Anaphylaxis is primarily an allergic reaction. Allergic reactions become anaphylaxis once an allergy begins to affect more than one body system, such as the skin and respiratory system. Anaphylaxis comes on suddenly and the symptoms progress quickly. It will develop most commonly after eating, getting stung by an insect, or taking medications.

What to Watch For

To identify anaphylactic shock, first look for symptoms of allergy which include:

  • Itching
  • Red, raised, blotchy skin, seen in 90 percent of cases
  • Wheezing or shortness of breath, seen in 70 percent of cases
  • Skin: You may have flushing and itching. Hives can develop, which are raised itchy bumps that blanch (turn white) when you press on them. Angioedema can develop, which is swelling under the skin.
  • Eyes: You may have signs of irritation including itching, redness, production of tears, and the skin may swell around the eyes.
  • Upper respiratory: Congestion, a runny nose, and sneezing can develop. You can feel throat swelling, choking, or hoarseness.
  • Oral: You may experience a swollen tongue, lips, or throat, or abnormal taste sensations.
  • Lower respiratory: You can have difficulty breathing, wheezing, and chest tightness
  • Circulatory: You may have a rapid or slow heartbeat and low blood pressure. You may feel dizzy, faint, or you may pass out.
  • Nervous system: You can become anxious or confused, have slurred speech, and may even feel a sense of impending doom.
  • Digestive system: Nausea, vomiting, diarrhea, or abdominal pain may be experienced.

Anaphylactic Shock

Anaphylaxis becomes anaphylactic shock when a person shows signs of low blood pressure:

  • Confusion
  • Weakness
  • Pale color
  • Unconsciousness

Anaphylactic shock often includes shortness of breath. A person doesn't always have trouble breathing, but if the symptom is present, it's a good indicator that the allergic reaction is turning into anaphylaxis.

Signs of Anaphylactic Shock

Some of the telltale signs include:

  • Unable to speak more than one or two words
  • Sitting straight up or with hands on knees
  • Gasping for breath
  • Pursing lips to breathe
  • Using neck muscles to take breaths

Allergen Exposure as a Sign

It's easier to identify the signs and symptoms of anaphylactic shock if there is a known allergen exposure. For instance, those with allergies to bee stings will usually know they've been stung.

Anyone who's had allergic reactions in the past should be aware of any symptoms, even if no allergen exposure has been identified. For example, people with food allergies are more likely to have anaphylaxis while eating even when they don't think they're eating the food they are allergic to.

If someone is wearing medical alert jewelry that indicates an allergy, that can help identify the cause of the symptoms.

Rare Symptoms 

An episode of anaphylaxis typically begins within 5 to 30 minutes of coming into contact with the allergen to which you are allergic, though it can take more than an hour.1However, there are atypical patterns. Symptoms can be seen in many parts of the body:1


Biphasic anaphylaxis is seen in up to 20 percent of patients, occurring in both children and adults, though it was once thought to be rarer. In this presentation, the initial anaphylactic reaction would manifest and it would resolve, only to have the reaction return hours to days later. This is why someone may be admitted to the hospital for observation after an anaphylactic reaction. In some cases, people won't experience the most severe symptoms of anaphylaxis, such as difficulty breathing, and thus decide not to seek medical care. However, this puts them at risk for a biphasic reaction, which can lead to severe consequences.

A study of pediatric cases published in 2015 found a higher incidence in children of age 6 to 9. They were more likely to have been treated with more than one dose of epinephrine, indicating they had a more severe reaction. They were also more likely to have had a delay in getting treatment with epinephrine or arriving at an emergency department.

Protracted anaphylaxis is seen rarely. In this case, the symptoms can last from several days to over a week without clearly resolving completely.