Symptoms of Anaphylaxis

Anaphylaxis is a sudden and severe allergic reaction that involves more than one body system. It is a life-threatening medical emergency. 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
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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

Symptoms can be seen in many parts of the body:

  • 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. However, there are atypical patterns.

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.


Anaphylaxis can result in death if not treated. A myocardial infarction or atrial fibrillation can develop during anaphylaxis, and these cardiac risks are greater in patients over the age of 50.

Epinephrine is the drug of choice to treat anaphylaxis, but it carries a risk of overdose and of triggering cardiovascular complications. In older patients, some research suggests it is safer to administer intramuscular injections rather than intravenous epinephrine.

When to See a Doctor

If you have any symptoms of anaphylaxis, get to medical care immediately. It is appropriate to call 911 for emergency treatment.

Don't wait to summon emergency care. The reaction can progress rapidly. Hives can turn into anaphylactic shock in minutes. If you are alone, you risk becoming unconscious before you can call for care.

If you know you are at risk of anaphylaxis from an allergy, call for emergency medical care as soon as you know you have been exposed. Even if you use an epinephrine self-injector, you will need emergency treatment.

Frequently Asked Questions

  • What causes anaphylaxis?

    Anaphylaxis is triggered by an allergen. Foods like nuts, fish, shellfish, and milk are allergens commonly linked to anaphylaxis in children. In adults, insect bites, latex, and certain medications are common causes of anaphylaxis in addition to foods.

  • How long does it take for anaphylaxis to occur?

    Anaphylaxis usually occurs between five to 30 minutes after coming into contact with an allergen. In some cases, it can take up to an hour or longer. Some people have delayed anaphylaxis and only experience symptoms several days later. Others have biphasic anaphylaxis, in which initial mild symptoms appear to resolve, only to return more severely within hours or days.

  • When is anaphylaxis life-threatening?

    Anaphylaxis can cause shock. This is a critical condition brought on by a sudden drop of blood flow throughout the body. Anaphylactic shock can cause death by restricting the amount of blood and oxygen that reaches organs, causing unconsciousness, coma, cardiac arrest, and even death. Anaphylaxis can also cause suffocation due to severe swelling of the throat. If left untreated, anaphylaxis can cause death within minutes to hours.

  • How is anaphylaxis treated?

    The first line of treatment for anaphylaxis is an injection of epinephrine, which relaxes smooth muscles and increases blood circulation. Cardiopulmonary resuscitation (CPR) may be needed if the affected person stops breathing. Other treatments may include:

    • High-flow oxygen therapy
    • Intravenous antihistamines to temper the allergic response
    • Intravenous corticosteroids to temper the overall immune response
    • A beta-agonist like albuterol to ease breathing
  • What can you expect after receiving treatment for anaphylaxis?

    If treated early and appropriately, anaphylaxis can usually improve within a few hours (although you may be admitted to the hospital for overnight observation). In severe cases, recovery may take several days. If not treated appropriately, anaphylaxis can cause permanent heart, brain, lung, and kidney injury.

  • Who should carry an anaphylaxis kit?

    Anyone with a history of anaphylaxis should carry an anaphylaxis kit, which includes an epinephrine auto-injector (called an EpiPen) and sometimes a strong oral antihistamine like diphenhydramine. You may also be advised to carry an anaphylaxis kit as well as a medical ID bracelet if you have a history of severe allergies. An allergist can advise you if you need one.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Academy of Allergy, Asthma & Immunology. Anaphylaxis

  2. Campbell RL, Bellolio MF, Knutson BD, et al. Epinephrine in anaphylaxis: higher risk of cardiovascular complications and overdose after administration of intravenous bolus epinephrine compared with intramuscular epinephrine. J Allergy Clin Immunol Pract. 2015;3(1):76-80. doi:10.1016/j.jaip.2014.06.007.

  3. Fischer D, Vander Leek TK, Ellis AK, Kim H. AnaphylaxisAllergy Asthma Clin Immunol. 2018;14(S2):54. doi:10.1186/s13223-018-0283-4

  4. Kim SY, Kim MH, Cho YJ. Different clinical features of anaphylaxis according to cause and risk factors for severe reactions. Allergol Int. 2018;67(1):96-102. doi:10.1016/j.alit.2017.05.005

  5. American Academy of Allergy, Asthma & Immunology. Anaphylaxis.

Additional Reading

By Rod Brouhard, EMT-P
Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.