Definition

An anaphylactic reaction is a severe and potentially life-threatening allergic response. While allergic symptoms are usually not life-threatening, severe allergic reactions can lead to anaphylaxis. There is a risk of experiencing an anaphylactic reaction upon re-exposure to the allergen, even if you or your child have experienced only mild anaphylactic reactions in the past.

Causes

The immune system produces antibodies that protect the body from foreign substances. This is beneficial when the foreign substance is harmful, such as certain bacteria or viruses. However, some people have an immune system that reacts excessively to substances that rarely cause allergic reactions. 

The most common triggers of anaphylaxis in children are food allergies, such as those to nuts, fish, shellfish, wheat, soy, sesame, and milk. Besides allergies to nuts, fish, and sesame, triggers of anaphylaxis in adults include:

1. Certain medications, such as antibiotics, aspirin, and other over-the-counter pain relievers, and contrast agents used for radiological examinations
2. Bee stings, wasp stings, and red ant bites
3. Latex

In rare conditions, some people experience anaphylactic reactions because of aerobic exercise, such as jogging, or even non-intensive physical activities like walking. Eating certain foods before exercise or engaging in physical activity during hot, cold, or humid weather has also been associated with anaphylaxis in some individuals. Discuss with your doctor what to be aware of during exercise.

If the trigger for an allergic reaction is unknown, various tests can be conducted to identify the allergen. In some cases, the cause of anaphylaxis may not be identified, which is referred to as idiopathic anaphylaxis.

Risk factor

There are not many known risk factors for anaphylaxis, but some things that can increase the risk include:

• Previous anaphylactic reactions: 

If you have experienced anaphylaxis once, your risk of experiencing this serious reaction increases. Subsequent reactions may be more severe than the first one.

• Allergies or asthma:

People who have either of these conditions are at a higher risk of experiencing anaphylaxis.

• Other specific conditions:

This includes heart disease and the accumulation of certain types of white blood cells (mastocytosis).

Symptoms

The symptoms of an anaphylactic reaction usually show up within a few minutes of coming into contact with an allergen. However, in some cases, anaphylaxis can happen half an hour or even later after being exposed to the allergen. Although rare, there are instances where the reaction may be delayed for several hours. The signs and symptoms of an anaphylactic reaction include the following: 

1. Skin reactions, such as hives, itching, and red or pale skin
2. Low blood pressure (hypotension)
3. Narrowing of the airways and swelling of the tongue or throat, leading to wheezing and difficulty breathing
4. Weak and rapid heartbeat
5. Nausea, vomiting, or diarrhea
6. Dizziness or fainting

Read more about hypotension: Hypotency - Definition, Cause, Symptom, And Treatment

Diagnosis

Doctors may inquire about previous allergic reactions, including a history of allergies to: 

1. Specific foods
2. Medications
3. Latex
4. Insect stings

These are several tests that help confirm the diagnosis:

1. You may undergo a blood test to measure certain enzymes (tryptase) that can increase up to 3 hours after anaphylaxis
2. You might be tested for allergies with skin tests or blood tests to help determine your triggers

When diagnosing anaphylaxis, the doctor will consider other conditions with similar signs and symptoms.

Management

During an anaphylactic reaction, you may require CPR if you have symptoms of shock, respiratory failure, or cardiac arrest. Medications that may also be administered include: 

1. Epinephrine (adrenaline) to reduce the body's allergic response
2. Oxygen to help you breathe
3. Injectable antihistamines and corticosteroids to reduce airway inflammation and improve breathing
4. Beta-agonists (such as albuterol) to alleviate respiratory symptoms

Many people at risk of anaphylaxis carry an autoinjector. This device consists of a syringe and needle containing a single dose of medication that is injected into the thigh. Using an autoinjector promptly can prevent the worsening of anaphylaxis and may save your life.

If insect stings trigger anaphylactic reactions, allergy shots (immunotherapy) can reduce the body's allergic response and prevent severe reactions in the future. Unfortunately, in most other cases, there is no specific treatment to address the immune system condition that leads to anaphylaxis.

Complications

Without prompt therapy, anaphylaxis can lead to: 

1. Blocked airways
2. Cardiac arrest
3. Respiratory failure
4. Shock

Read more: Pulmonary Heart Arrest - Definition, Cause, Symptoms, And Treatment

Prevention

The best way to prevent anaphylaxis is to avoid substances that trigger this severe reaction. Additionally, here are some things you can do: 

1. Use a medical alert bracelet or necklace to indicate that you have an allergy to specific drugs or other substances
2. Ensure that an emergency kit with prescribed medications is available at all times. Your doctor can advise and make sure this kit contains complete medications. If you have an epinephrine autoinjector, check its expiration date and replace it before it expires. Make sure you know how to use it. Also, ensure your family member or anyone who lives close to you also knows how to use the kit
3. Inform your doctor about any past reactions to medications 
4. If you are allergic to stinging insects, be cautious when near them. Wear long-sleeved clothing and long pants; avoid walking in grass without shoes; and refrain from using perfumes or scented lotions. Remain calm when moving near stinging insects. Move away slowly and do not make sudden moves or trigger the insects
5. If you have a food allergy, read the labels of all the food you buy and eat carefully. Manufacturing processes can change, so it's essential to recheck the labels of foods that you regularly consume.

When to see a doctor?

Seek immediate medical help if you, your child, or someone else with you experiences a severe allergic reaction. Do not wait to see if the symptoms improve.

If you experience an anaphylactic reaction and have an epinephrine autoinjector, administer it immediately. Even if symptoms improve after the injection, you still have to go to the emergency room to ensure that your symptoms do not recur, even without continued exposure to the allergen. This second reaction is called biphasic anaphylaxis.

If you find someone else experiencing signs and symptoms of pale, cold, and moist skin, a weak and rapid pulse, difficulty breathing, confusion, or unconsciousness, do the following:

1. Call an emergency service
2. Use an epinephrine autoinjector, if available, by injecting it into the person's thigh
3. Ensure the person lies down with their legs elevated higher than the heart and head
4. Check their pulse and breathing, and perform CPR or other first aid if necessary. If you do not know how to do it, wait until help arrives

Consulting an allergy and immunology specialist may be necessary to diagnose and manage long-term anaphylaxis effectively.

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