In anaphylactic shock, the substance which causes dilation of blood vessels and capillary leakage is

Options

A. Adrenaline
B. Benadryl
C. Albumin
D. Histamine

Answer

**Step-by-Step Solution:**

1. **Understanding Anaphylactic Shock**: Anaphylactic shock is a severe allergic reaction that occurs rapidly after exposure to an allergen. It can lead to life-threatening symptoms, including difficulty breathing, swelling, and a drop in blood pressure.

2. **Identifying the Role of Allergens**: Allergens are substances that trigger allergic reactions. When a person is exposed to an allergen, their immune system may overreact.

3. **Involvement of Basophils and Mast Cells**: Upon exposure to allergens, certain immune cells known as basophils and mast cells become activated. These cells are crucial in the allergic response.

4. **Release of Histamine**: When activated, basophils and mast cells release various chemicals, one of the most significant being histamine. Histamine is a biogenic amine that plays a key role in allergic reactions.

5. **Effects of Histamine**: Histamine causes vasodilation (widening of blood vessels) and increases the permeability of blood vessel walls. This leads to symptoms such as swelling, redness, and a drop in blood pressure, which are characteristic of anaphylactic shock.

6. **Conclusion**: The substance responsible for the dilation of blood vessels and capillary leakage during anaphylactic shock is histamine.

**Final Answer**: Histamine is the substance that causes dilation of blood vessels and capillary leakage in anaphylactic shock.

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