In most cases, people with allergies develop mild to moderate symptoms, such as watery eyes, a runny nose or a rash. But sometimes, exposure to an allergen can cause a life-threatening allergic reaction known as anaphylaxis. Allergies to food, insect stings, medications and latex are most frequently associated with anaphylaxis.  The immune system produces antibodies that defend against foreign substances. This is good when a foreign substance is harmful, such as certain bacteria or viruses. But some people’s immune systems overreact to substances that don’t normally cause an allergic reaction.  This severe, potentially life-threatening reaction happens when an over-release of natural chemicals such as histamine puts the person into shock. It can occur within seconds or minutes of exposure to something to which you are allergic. Sometimes, however, anaphylaxis can occur a half-hour or longer after exposure and in rare cases, anaphylaxis may be delayed for hours.  Delayed reactions are most typically seen in children who develop eczema as a symptom of food allergy and in people with a rare allergy to red meat caused by the bite of a lone star tick. If anaphylaxis isn’t treated right away, it can be fatal.

Signs and symptoms

Anaphylaxis symptoms occur suddenly and can progress quickly. The early symptoms may be mild, such as a runny nose, a skin rash or a “strange feeling.” These symptoms can quickly lead to more serious problems, including:

  • Skin reactions – hives, itching, swelling or pale skin
  • Runny nose, itchy eyes, sneezing
  • Tightness of the throat, swollen tongue
  • Hoarse voice
  • Shortness of breath, Wheezing,
  • Nausea, vomiting or diarrhea. Abdominal cramping
  • Chest pain
  • Low blood pressure
  • A weak and rapid pulse (heartbeat)
  • Dizziness or fainting

Risk factors

There aren’t many known risk factors for anaphylaxis, but some things that might increase the risk include:

  • Previous anaphylaxis. If you’ve had anaphylaxis once, your risk of having this serious reaction increases. Future reactions might be more severe than the first reaction.
  • Allergies or asthma. People who have either condition are at increased risk of having anaphylaxis.
  • Certain other conditions. These include heart disease and an irregular accumulation of a certain type of white blood cell (mastocytosis).


  • The best way to prevent anaphylaxis is to stay away from substances that cause this severe reaction. Also:
  • Be prepared. Prompt recognition of the signs and symptoms of anaphylaxis is critical.
  • Wear a medical alert necklace or bracelet to indicate you have an allergy to specific drugs, foods or other substances.
  • Tell family and friends. Family and friends should be aware of your condition, your triggers and know how to recognize anaphylactic symptoms. If you carry epinephrine, alert them to where you keep it and how to use it.
  • Epinephrine is the first-line treatment for anaphylaxis. Once you have been diagnosed with anaphylaxis you should be prescribed an epinephrine auto-injector and be taught how to use it.
  • You should also be given a written treatment plan describing what medications you have been prescribed and when they should be used.
  • Keep an emergency kit with prescribed medications available at all times. Your provider can advise you on the contents. Check the expiration date and be sure to refill the prescription before it expires.
  • Be sure to alert all your providers to medication reactions you’ve had.
  • If you’re allergic to stinging insects, use caution around them.
  • If you have food allergies, carefully read the labels of all the foods you buy and eat. Manufacturing processes can change, so it’s important to periodically recheck the labels of foods you commonly eat.
  • When eating out, ask how each dish is prepared, and find out what ingredients it contains. Even small amounts of food you’re allergic to can cause a serious reaction.

When to see a doctor

Seek emergency medical help

  • If you, your child or someone else you’re with has a severe allergic reaction. Don’t wait to see if the symptoms go away.
  • If you have an attack and you carry an epinephrine autoinjector, administer it right away.
  • If an expired auto-injector is the only one available in an emergency situation, administer it promptly anyway.
  • Call 911 and get to the nearest emergency facility at the first sign of anaphylaxis, even if you have already administered epinephrine
  • Even if symptoms improve after the injection, you still need to go to an emergency room to make sure symptoms do not recur (even without more exposure to the allergen).

Common side effects of epinephrine may include anxiety, restlessness, dizziness and shakiness. In very rare instances, the medication can lead to abnormal heart rate or rhythm, heart attack, an increase in blood pressure and fluid buildup in the lungs. If you have certain pre-existing conditions, such as heart disease or diabetes, you may be at a higher risk for adverse effects from epinephrine. Nevertheless, epinephrine is considered very safe and is the most effective medicine to treat severe allergic reactions. Other medications may be prescribed to anaphylaxis, but it is important to note that there is no substitute for epinephrine: It is the only medication that can reverse the life-threatening symptoms of anaphylaxis.

Make an appointment to see a provider

The diagnosis and long-term management of anaphylaxis can be complicated, so you will probably need to see a doctor who specializes in allergies and immunology.

If you don’t know what triggers an allergy attack, certain tests (such as skin-prick tests, blood tests and oral food challenges) can help identify the allergen. In some cases, the cause of anaphylaxis is not identified (idiopathic anaphylaxis).

Consider Allergy consultation if:

  • You’re unsure whether you have had an anaphylactic reaction.
  • Your symptoms are recurring or are difficult to control.
  • You are having trouble managing your condition.
  • More tests are needed to determine the cause of your reactions.
  • Desensitization or immunotherapy could be helpful in your case.
  • Daily medication is needed.
  • You need more education on avoidance and anaphylaxis management.
  • Other medical conditions complicate your treatment.

Signs & Symptoms of Anaphylaxis

  • Hives
  • Intense itching
  • Nasal congestion
  • Facial swelling
  • Shortness of breath
  • Wheezing
  • Lightheadedness
  • Chest pain
  • Palpitations
  • Abdominal cramping
  • Nausea, Vomiting & Diarrhea