Anaphylaxis is a severe, life-threatening allergic reaction that can occur when the body’s immune system overreacts to a foreign substance. This foreign substance, known as an allergen, can be anything from food to medication to insect venom.

When a person is exposed to an allergen for the first time, the immune system produces antibodies called immunoglobulin E (IgE). These antibodies attach to mast cells and basophils, which are white blood cells that release chemicals called histamine and other mediators when they are activated.

If the person is exposed to the allergen again, the IgE antibodies will bind to the allergen and cause the mast cells and basophils to release histamine and other mediators. These mediators cause a number of changes in the body, including:

• Vasodilation: This causes the blood vessels to widen, which leads to a decrease in blood pressure.
• Increased vascular permeability: This causes the blood vessels to leak fluid, which can lead to swelling and tissue damage.
• Smooth muscle contraction: This can cause narrowing of the airways, which can lead to difficulty breathing.
• Bronchoconstriction: This causes the airways to narrow, which can also lead to difficulty breathing.
• Urticaria: This is a rash that is caused by swelling of the skin.
• Angioedema: This is a swelling that is caused by fluid leaking from the blood vessels into the tissues.

In severe cases, anaphylaxis can lead to death.

The pathophysiology of anaphylaxis is complex and not fully understood. However, it is thought that the release of histamine and other mediators from mast cells and basophils is the main cause of the symptoms. These mediators cause a number of changes in the body, including vasodilation, increased vascular permeability, smooth muscle contraction, bronchoconstriction, urticaria, and angioedema. These changes can lead to a decrease in blood pressure, difficulty breathing, and swelling of the skin and tissues.

In some cases, anaphylaxis can be triggered by a single exposure to an allergen. However, it is more common for anaphylaxis to occur after multiple exposures to the allergen. This is because the body becomes more sensitive to the allergen each time it is exposed.

There is no cure for anaphylaxis, but it can be treated with epinephrine, which is a medication that reverses the effects of the allergic reaction. Epinephrine can be given by injection or by inhalation.

If you have a history of anaphylaxis, it is important to carry an epinephrine auto-injector with you at all times. This will allow you to treat anaphylaxis quickly if it occurs.

Here are some additional thoughts on the pathophysiology of anaphylaxis:

• Anaphylaxis is a serious medical emergency. If you think you are having an anaphylactic reaction, it is important to seek medical attention immediately.
• There are a number of things that can trigger anaphylaxis. These include food, medication, insect venom, latex, and exercise.
• There is no way to predict who will develop anaphylaxis. However, people who have a history of allergies are more likely to develop anaphylaxis.
• There are a number of things that can be done to prevent anaphylaxis. These include avoiding known allergens, carrying an epinephrine auto-injector, and being aware of the signs and symptoms of anaphylaxis.