The release of which of the following in the body causes allergy ?

Options

A. Hydrochloric acid
B. Protaglandins
C. Noradrenaline
D. Histamine

Answer

To determine which substance released in the body causes allergies, we can analyze the options provided: Hydrochloric acid, Prostaglandins, Noradrenaline, and Histamine.

### Step-by-Step Solution:

1. **Understanding Hydrochloric Acid**:
- Hydrochloric acid (HCl) is produced in the stomach and is primarily involved in digestion. It helps break down food and maintain an acidic environment in the stomach.
- **Conclusion**: Hydrochloric acid is not related to allergies.

2. **Understanding Prostaglandins**:
- Prostaglandins are lipid compounds that are involved in the inflammatory response and help in dealing with injuries and infections. They play a role in processes such as inflammation and blood flow regulation.
- **Conclusion**: Prostaglandins are not directly related to allergies.

3. **Understanding Noradrenaline**:
- Noradrenaline (or norepinephrine) is a hormone and neurotransmitter that plays a role in the body's fight-or-flight response. It helps regulate blood pressure and is not involved in allergic reactions.
- **Conclusion**: Noradrenaline does not cause allergies.

4. **Understanding Histamine**:
- Histamine is an organic nitrogenous compound that is released during immune responses, particularly in response to allergens. It is responsible for symptoms of allergies such as itching, swelling, and redness.
- **Conclusion**: Histamine is directly involved in causing allergies.

5. **Final Answer**:
- Based on the analysis, the substance that causes allergies upon release in the body is **Histamine**.