Anesthesia Allergy: Causes, Symptoms, & Reducing Your Risk

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Anesthesia is a treatment that uses medications to prevent a patient from feeling pain during a medical procedure, such as surgery, diagnostic testing, or dental procedures. There are several ways anesthesia is used to prevent pain, including general, regional, and local anesthesia. General anesthetics put people to sleep during procedures, while regional and local anesthesia prevents pain while the patient is awake.

While what are known as "hypersensitivity reactions" to medical procedures can occur, anesthesia allergy is not very common. This article reviews the causes and symptoms of an anesthesia allergy and tips for decreasing risk.

Women going under anesthesia for surgery

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Symptoms

Allergic reactions occur when the immune system overreacts to what is an otherwise harmless substance. Allergic reactions can range from mild to severe and, in extreme cases, can even be deadly.

Some of the most common allergic reaction symptoms to anesthesia include:

  • Skin rash
  • Itching
  • Hives
  • Swelling of the face, tongue, or lips

The most severe and deadly form of anesthesia allergy is called anaphylaxis. During anaphylaxis, the immune system reacts to the anesthesia by releasing chemicals that cause symptoms, such as:

  • Light-headedness or faintness
  • Fast and shallow breathing
  • A too fast or too slow heartbeat
  • Wheezing
  • Confusion
  • Clammy skin
  • Loss of consciousness
  • Nausea, vomiting, or diarrhea

Anaphylactic shock is a life-threatening condition that requires immediate medical treatment, which includes an injection of a medication called epinephrine. Unfortunately, when a patient is under general anesthesia, it may be more difficult for a healthcare provider to know that they are experiencing anaphylactic shock.

Fortunately, anaphylaxis to anesthesia is very rare, affecting about 1 in 5,000 to 25,000 patients.

Hypersensitive Reactions

The World Allergy Organization (WAO) reports that immediate hypersensitivity reactions after medical procedures occur in 1 out of every 1,250 to 10,000 people. The WAO also notes that 60% of these hypersensitivity reactions are allergic reactions to medication.

Causes

Some people may have a negative immune response to substances that most people don't. Allergies are the body's overactive response to a harmless substance it sees as a potential threat. Common allergens include medications, food, dust, or mold.

One of the roles of the immune system is to destroy harmful substances in the body and protect it from disease. Under normal circumstances, our immune system targets germs that can potentially hurt us, such as viruses, bacteria, and toxins.

If someone is allergic to a substance, the immune system produces chemicals called antibodies to fight the allergen. This reaction causes allergy symptoms.

Nonallergic Reactions to Anesthesia

Anesthesia can cause unpleasant and occasionally serious side effects. It's essential to understand that those side effects are not the same as an allergic reaction.

Allergic reactions are when your body's immune system overreacts to a substance, while side effects are unwanted effects that are not related to the immune system.

General Side Effects

General side effects of anesthesia are temporary and usually resolve within 24 hours. Potential side effects of anesthesia include:

  • Headache
  • Sleepiness
  • Back pain or muscle pain
  • Chills, also known as hypothermia
  • Difficulty urinating
  • Itching
  • Nausea and vomiting
  • Discomfort or bruising at the injection site

Malignant Hyperthermia

Malignant hyperthermia is a life-threatening but rare reaction to anesthesia characterized by an unusually high body temperature. Symptoms can include:

  • Muscle contractions
  • Fever
  • Fast heart rate
  • Breakdown of muscle fibers, called rhabdomyolysis

Immediate treatment and discontinuation of anesthetic medication for malignant hyperthermia is essential. When a person has malignant hyperthermia, their body can react in several ways, including:

Inform Your Provider

If you or a loved one has ever experienced a heart attack or other side effect after anesthesia, be sure to inform your healthcare provider before receiving anesthesia.

Pseudocholinesterase Deficiency

Pseudocholinesterase deficiency is a condition causing a patient to be very sensitive to certain muscle relaxant medications used in anesthesia.

Muscle relaxants, or neuromuscular blocking agents (NMBAs), are medications commonly used to keep patients still and calm during medical procedures. This type of anesthetic is most commonly used during intubation and mechanical ventilation.

Under normal circumstances, the medications are broken down very quickly, usually within a few minutes. But with pseudocholinesterase deficiency, patients don't metabolize the medication for a much longer time, sometimes even for several hours.

Muscle relaxants also cause the diaphragm, a thin skeletal muscle at the base of the chest, to relax and make it difficult for people to breathe independently. These patients may require mechanical ventilation to help them breathe until the drugs have metabolized.

Reducing Your Risk of an Allergic Reaction

During surgery, anesthesiologists commonly use many different drugs to keep patients comfortable and safe. However, some people are more sensitive to the medicines than others. Also, some people are more likely to have anaphylaxis than others.

If you have a personal or family history of allergies or anaphylaxis, talk to your provider about anesthesia allergy risks. A history of allergies puts you at a higher risk of allergy to medications used for anesthesia during medical procedures.

Identifying risks before surgery will help your provider plan accordingly and be alert to potential allergic reactions during and after surgery.

Summary

Anesthesia is a medical treatment using drugs to prevent a patient from feeling pain during a medical procedure like surgery. Allergic reactions to anesthetics can occur, though they are very rare. Some of the most common allergic reactions to anesthetics are skin rash, itching, and swelling of the face, tongue, or lips. Anaphylactic shock is possible and requires immediate medical attention.

Identifying risks before surgery will help your healthcare provider plan accordingly, so be sure to inform them of any allergies or previous reactions to anesthesia.

A Word From Verywell 

Having a medical procedure that requires anesthesia can be a frightening experience. Fortunately, allergies to anesthetics are very rare. There are also treatments available to help if you have one.

If you or a loved one has a medical procedure requiring anesthesia, talk to your healthcare provider about allergy or anaphylaxis risks. A history of allergies puts you at a higher risk of having an allergy to anesthesia medication during medical procedures.

Frequently Asked Questions

  • What happens if you’re allergic to anesthesia?

    If you have a mild allergy to anesthesia, your provider may recommend an antihistamine, such as diphenhydramine (also known as Benadryl). However, anaphylactic shock is a life-threatening condition requiring immediate medical treatment (an injection of a medication called epinephrine).

  • Is it common to be allergic to anesthesia?

    Anesthesia allergy is rare. The World Allergy Organization (WAO) reports that immediate "hypersensitivity reactions" after medical procedures occur in 1 out of every 1,250 to 10,000 people. They also state that 60% of these hypersensitivity reactions are allergic reactions to medication.

  • How do you know if you are allergic to local anesthesia?

    Some of the most common allergic reactions to local anesthesia include:

    • Skin rash
    • Itching
    • Hives
    • Swelling of the face, tongue, or lips

    You can also make an appointment with an immunologist or allergist, who are highly trained professionals in allergy diagnosis and management.

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7 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. National Institute of General Medical Sciences. Anesthesia.

  2. John Hopkins Medicine. Allergies and the immune system.

  3. Canadian Anesthesia Society. Allergic reactions during surgery.

  4. World Allergy Organization. Perioperative allergic reaction.

  5. American Society of Anesthesiologists. Effect of anesthesia.

  6. MedlinePlus. Malignant hyperthermia.

  7. MedlinePlus. Pseudocholinesterase deficiency.