Also known as Severe allergic reaction, Hypersensitivity reaction, Anaphylactic shock and Allergic shock

Overview

Anaphylaxis is a severe, life-threatening allergic reaction that can affect multiple systems of the body at the same time. Common triggers of this reaction include certain foods, insect stings, some medications, or latex. However, anaphylaxis is rare. The majority of people, even those with allergies, might never suffer from an episode of anaphylaxis.

The symptoms of anaphylaxis include tongue swelling, vomiting, difficulty in breathing, mental confusion and even shock. These symptoms occur due to over reaction of the immune system.

People with allergies, asthma and a family history of anaphylaxis are at a higher risk of anaphylaxis. If someone is at a higher risk or has a known serious allergy, avoidance is the best form of treatment.

Anaphylaxis requires immediate medical treatment because if it is not treated timely or properly, it can be fatal. If someone has a history of a serious allergic reaction, it is important to always carry an adrenaline(epinephrine) kit.

Accurate diagnosis and successful management of allergies is essential to prevent any  anaphylactic reactions in the future. An allergist or immunologist, has specialized training and experience to diagnose the problem and develop a prevention plan. 

Key Facts

Usually seen in

  • Infants between 0-2 years of age

Gender affected

  • Both men and women but more common in women

Body part(s) involved

  • Skin
  • Respiratory system
  • Gastrointestinal system
  • Cardio-vascular system
  • Central nervous system

Prevalence

  • Worldwide: 0.3–5.1% (2020)
  • India: 0.14% (2020)

Mimicking Conditions

  • Acute asthma 
  • Peri-menopause
  • Syncope (faint) 
  • Carcinoid syndrome
  • Anxiety/panic attack
  • Autonomic epilepsy
  • Acute generalized urticaria 
  • Medullary carcinoma of the thyroid
  • Aspiration of a foreign body 
  • Non Organic Disease
  • Myocardial infarction
  • Pulmonary embolism
  • Vocal cord dysfunction
  • Seizure
  • Cerebrovascular event
  • Hyperventilation
  • Psychosomatic episode
  • Scombroidosis shock
  • Pollen-food allergy syndrome 
  • Hypovolemic shock
  • Sulfites distributed
  • Food poisoning 
  • Sepsis
  • Excess endogenous histamine 
  • Non Allergic angioedema
  • Basophilic leukemia 
  • Hereditary angioedema types I, II, & III
  • ACE inhibitor-associated angioedema
  • Systemic capillary leak syndrome
  • Red man syndrome (vancomycin)
  • Pheochromocytoma (paradoxical response)

Necessary health tests/imaging

  • Laboratory tests: Skin prick testing, Serum-specific IgE, and Serum enzyme tryptase

Treatment

Symptoms Of Anaphylaxis


As anaphylaxis is a generalized systemic reaction, a wide variety of clinical signs and symptoms involving the skin, gastrointestinal and respiratory tracts, and cardiovascular system can be observed. The most common clinical manifestations include:

  • Cutaneous (skin) symptoms: 
    • Red, hot, and itchy rashes
    • Pale and cold skin
    • Urticaria (skin rashes)
  • Respiratory symptoms:
    • Wheezing
    • Stridor (high pitched sound on respiration)
    • Difficulty in breathing
    • Gasping
    • Bronchospasm (tightness of muscles lining the lungs)
  • Cardiovascular symptoms:
    • Tachycardia (increased heart rate) 
    • Hypotension (low blood pressure)
    • Bradycardia (decreased heart rate)
  • GI symptoms:
    • Nausea
    • Vomiting
    • Abdominal pain
    • Diarrhea
  • Neurological symptoms:
    • Lightheadedness
    • Confusion
    • Loss of consciousness
  • Conjunctival (eye) symptoms
    • Erythema (redness)
    • Pruritus (itching)
    • Excessive tearing
  • Other symptoms
    • Sense of impending doom
    • Tingling
    • Anxiety
    • Metallic taste in the mouth
    • Laryngeal edema (swelling in the throat)
    • Uterine cramps and bleeding

Causes Of Anaphylaxis


Anaphylaxis is generally caused by triggers and it’s very important to know what triggered the reaction. The most common triggers include:

1. Food

Food allergies are quite common and in severe cases, they can precipitate an anaphylactic reaction. Common food items that can cause anaphylaxis include

  • Peanuts
  • Walnuts
  • Pecans
  • Fish
  • Shellfish
  • Cow’s milk
  • Eggs
  • Red meat
  • Prawns
  • Shrimps 
  • Lobster

2. Medications

When your immune system mistakenly identifies a medication as a harmful substance, it will develop an antibody specific to that drug leading to an allergic reaction. Medications that can cause anaphylaxis include:

  • Antibiotics
    • Penicillin
    • Cephalosporin
    • Other Antibiotics
  • NSAIDS
    • Diclofenac
    • Disprin
    • Paracetamol
  • Drugs used in anesthesia
  • Eugenol
  • Muscle relaxants
  • β-adrenergic blocker
  • ACE inhibitor

3. Latex

Latex allergy may cause itchy skin and hives or even anaphylaxis, a potentially life-threatening condition that can cause throat swelling and severe difficulty breathing. It is generally used in the following:

  • Disposable gloves
  • Intravenous tubes
  • Syringes
  • Adhesive tapes
  • Catheters

4. Insect stings

Episodes of anaphylaxis can also occur following insect stings or bites. Insects that are most likely to trigger anaphylaxis are:

  • Bees
  • Wasps
  • Hornets
  • Yellowjackets
  • Fire ants 

5. Vaccines

Some patients can also develop anaphylaxis following immunization. The majority of cases of vaccine-associated anaphylaxis include vaccination from:

  • Measles, mumps, and rubella (MMR) vaccine
  • Japanese encephalitis vaccine
  • Diphtheria, tetanus, and pertussis (DPT)
  • Hepatitis A and B vaccine

Risk Factors For Anaphylaxis


Anaphylaxis is a life-threatening type I hypersensitivity reaction, triggered by exposure to a wide range of antigens that involve multiple organ systems. Risk factors for anaphylaxis include:

1. Cardiovascular diseases

Preexisting cardiovascular disease is a risk factor for fatal anaphylactic reactions or lasting morbidity due to myocardial infarction (heart attack) or stroke induced by anaphylaxis.

2. Asthma

Poor asthma control remains a risk factor for severe anaphylaxis, especially in children.

Want to know the basics of asthma? The second Tuesday of May is observed as World Asthma Day with the aim to raise awareness about the condition and its management.

3. Mastocytosis

It is a rare condition caused by an excess number of mast cells (a type of immune cells) gathering in the body’s tissues. Adult patients and children with extensive skin disease with mastocytosis have an increased risk to develop severe anaphylaxis.

4. Age

It has been observed that the first anaphylactic episode mostly occurs in the age group 0–2 years. Also, older age has been consistently associated with a higher rate of fatal drug anaphylaxis.

5. Previous anaphylactic reaction

The risk of serious reaction increases if you’ve had anaphylaxis once and future reactions might be more severe than the first reaction.

6. Gender

Adult women suffer more frequently from anaphylaxis induced by food, drugs, and radiocontrast agents along with idiopathic anaphylaxis compared to adult men.

7. Alcohol

Allergy to alcohol can cause symptoms ranging from mild, such as an itchy mouth or eyes, to severe, including vomiting or anaphylaxis.

8. Exercise

Exercise-induced anaphylaxis is a rare but potentially life-threatening clinical syndrome in which association with exercise is crucial. The range of physical activities can be as mild as walking. 

Diagnosis Of Anaphylaxis


To diagnose your risk of anaphylaxis or to determine whether previous symptoms were anaphylaxis-related, your allergist/immunologist will conduct a thorough investigation of all potential causes that include:

Medical history

Your allergist will ask for specific details regarding all past allergic reactions. Clinical history along with allergy testing is used in the identification of allergen triggers.

Laboratory tests

Medically supervised allergen challenges may also be undertaken to confirm a diagnosis or determine if a patient has outgrown an allergy. Tests to identify sensitization to an allergen include:

1. Skin prick test (puncture or scratch test): This test inspects for immediate allergic reaction to different allergens at the same time. It is usually performed on the forearm in adults and on the upper back in children.



2. Serum-specific IgE: This test was formerly known as RAST(Radioallergosorbent testing). It measures how much IgE your body makes in response to a single allergen and is preferred when skin prick test (the favored allergy test) is not suitable or not available.  

3. Serum enzyme tryptase: Tryptase is released from mast cells during anaphylaxis. The level can be raised for three hours after the reaction. Levels greater than 11.5 ng/mL are considered elevated.

4. SC5b-9 (soluble membrane attack complex (sMAC) or terminal complement complex (TCC)): This test measures the complement system activation which can be elevated shortly after a severe allergic reaction. 

Note: Testing for allergen-specific IgE food mixes is not recommended as it does not indicate which foods from the mix the patient is allergic to and may result in unnecessary avoidance of foods.

Prevention Of Anaphylaxis


If you have a serious allergy or have experienced anaphylaxis in the past, it’s important to try to prevent any future episodes. It can be done by keeping the following things in mind:

Identify the triggers

Finding out what you are allergic to, can help you avoid these future episodes of anaphylaxis. 

Avoid those triggers

If a trigger has been identified, you’ll need to take steps to avoid it in the future whenever possible. Here are some of the most common triggers and ways to avoid them:

1. Food

  • Check the food labels for ingredients
  • Let the staff at a restaurant know what you’re allergic to so it’s not included in your meal
  • Remember what types of food may contain small traces of potential allergens 


2. Insect stings

  • Move away from wasps, hornets or bees slowly without panicking
  • Use an insect repellent if you spend time outdoors, especially in the summer
  • Be careful drinking out of cans when there are insects around
  • Do not walk around outside with bare feet


3. Medicines

  • If you’re allergic to certain types of medicines, talk to your doctor to prescribe alternatives that can be safely used.

Always carry adrenaline auto-injectors

You may be prescribed an adrenaline auto-injector if there’s an ongoing risk you could develop anaphylaxis. Things to keep in mind while using an auto-injector are:

  • Always carry two in-date auto-injectors at all times 
  • Make sure you and any caregivers know when and how to use your auto-injector
  • Check the expiry date regularly and replace it before it expires 
  • Do not delay injecting yourself if you think you may be experiencing anaphylaxis

Specialist To Visit


You should contact the emergency department of your nearest hospital if you suffer from an anaphylactic attack. Doctors that can help you with this are:

  • General physician
  • Allergist
  • Immunologist


An allergist is a medical practitioner specializing in the diagnosis and treatment of allergies. An immunologist is a doctor who diagnoses, treats, and works to prevent immune system disorders.

Treatment Of Anaphylaxis


The treatment of anaphylaxis depends upon the ability of the patient to describe the situation but if the patient is unconscious or not properly conscious, understanding the symptoms becomes important. Anaphylaxis treatment includes:

Medications

The medications used to treat an anaphylactic reaction include:

  • Adrenaline (Epinephrine): This is the first line of treatment recommended for patients with anaphylaxis. This drug can be life-saving as it plays an important role in delaying the progression of life-threatening reactions.
  • Antihistamines: Antihistamines reduce inflammation in air passages and also improve breathing. H1 antihistamines such as diphenhydramine or cetirizine can also relieve itching and hives.
  • Beta antagonist: They are used for airways protection and to relieve respiratory tract symptoms.
  • Glucocorticoids: Steroids (glucocorticoids) are often recommended in anaphylaxis. They reduce the severity of the acute reaction and the risk of recurrence.

For hospital-based patients

Patients who have been moved to a hospital set up and stabilized, the following agents are used:

  • Activated charcoal: The solution is commonly used to treat poison victims, and also to treat people with peanut allergies. Drinking activated charcoal immediately after accidental exposure to peanuts can block further absorption of allergy-causing proteins in the body and reduce the severity of the allergic reaction.
  • Vasopressors: Norepinephrine, vasopressin and other pressors are helpful in patients suffering from anaphylaxis with refractory hypotension (persistent hypotension in resuscitated patients)
  • Glucagon: It is an anti-hypoglycemic used to manage and treat anaphylaxis refractory to epinephrine, and aid in passing food boluses. 
  • Intravenous fluids: These are administered to maintain adequate blood circulation.

In case of emergency

If you are with someone who is having an allergic reaction with signs of anaphylaxis, here are things you need to do:

  • Call the local medical emergency number immediately.
  • See If the person is carrying an epinephrine auto-injector (EpiPen, Auvi-Q, others) to treat an allergic attack.
  • Help the person inject the medication by pressing the autoinjector against the person’s thigh.
  • Make the person lie face up and be still.
  • Loosen their tight clothing and cover the person with a blanket. 
  • Turn the person to the side to prevent choking if there’s vomiting or bleeding from the mouth.
  • Position the patient in the Trendelenburg position i.e lying flat on the back with legs elevated in order to allow blood flow to the heart.
  • If there are no signs of breathing, coughing or movement, begin CPR (start uninterrupted chest presses about 100 every minute).

Complications Of Anaphylaxis

Anaphylactic shock is an extremely serious condition that can block your airways and prevent you from breathing. It can also stop your heart. This is due to the decrease in blood pressure that prevents the heart from receiving enough oxygen. The complications of anaphylaxis include:

  • Cerebral hypoxia: It refers to a condition in which there is a decrease of oxygen supply to the brain even though there is adequate blood flow.
  • Acute renal failure: It is associated with anaphylactic shock caused by diclofenac sodium.
  • Fetal death: There is no evidence that anaphylaxis occurs in the fetus but maternal anaphylaxis can lead to a significant risk of fetal/neonatal neurological damage or even death.
  • Septic shock: It is caused by malfunction of the vascular system due to severe allergic reactions such as anaphylaxis that results in blood poisoning by bacteria.
  • Acute respiratory distress syndrome: It is a condition in which fluid collects in the air sacs of the lungs, depriving organs of oxygen.
  • Abnormal coagulation profile: Anaphylaxis is a complex allergic reaction where multiple biological systems are involved and it can lead to disruption of coagulation systems in severe cases.
  • Pulmonary edema: Histamines are the substances released by the body during an allergic reaction, that cause the blood vessels to expand, which in turn causes a dangerous drop in blood pressure. Fluid can leak into the lungs, causing swelling (pulmonary edema).
  • Arrhythmia: Anaphylaxis can also cause heart rhythm disturbances.
  • Abnormal liver function: The relationship between acute liver injury with idiopathic anaphylaxis is rare, but there are cases involving repeated episodes of anaphylactic shock accompanied by acute liver injury.

Alternative Therapies For Anaphylaxis

Homeopathy

Homeopathy works by correcting the immune responses of individuals rather than suppressing or modifying the immune system. Some individuals use homeopathic remedies for allergic reactions or allergic diseases, but there is no research showing effectiveness of homeopathy in preventing or treating anaphylaxis. Anaphylaxis requires emergency medical treatment.

Acupuncture

Acupuncture has been used to support the immune system and to relieve symptoms of seasonal allergies. However, acupuncture should not be used to treat anaphylaxis, which requires immediate medical attention.

Traditional chinese medicine (TMC)

TCM has been used in China and other Asian countries for thousands of years, either as monotherapy or in combination with standard Western medical treatment. Studies suggest that an herb-based formula (FAHF-2) may be an effective approach to food allergy treatment that is not specific to any one food allergen and can be potentially used to treat multiple food allergies.

Living With Anaphylaxis

A number of general strategies and tips may help you or your child avoid anaphylaxis, or improve health outcomes when a reaction happens. Some of them include:

Anaphylaxis education

Awareness of people about anaphylaxis, their family, and caregivers tend to decrease distress and apprehension and instills trust in their capacity to cope, not just by anaphylactic episodes but even by identification and timely treatment. 

Keep a close watch on the food ingredients

If you have a severe food allergy, scan food labels carefully for any troublesome ingredients, which may be harmful.You should also feel free to ask detailed questions about ingredients and food preparation when you’re eating out.

Introduce new foods to children slowly

If you or your child have had a severe allergic reaction to a food, it’s more likely that another new food will also cause problems. This might require sensitization, which means that the first few times your child tries out a new food item, give it in small amounts with bites that are spaced out.

Always wear a medical ID tag

Having a necklace or bracelet that indicates your anaphylaxis risk can help bystanders and first responders identify what’s happening to you in case of any reaction or emergency.

Keep all potential treatments handy

These include an epinephrine auto-injector for nearly everyone, and also possibly a chewable antihistamine and a stiff card to scrape out a bee’s stinger.

Never share your epinephrine

You shouldn’t use your auto-injector on anyone else unless you know for sure that they are having an anaphylactic reaction. Doing so not only may put you at risk for not having this treatment available for you, but it may cause medical problems in someone who isn’t experiencing anaphylaxis.

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