Agents which cause allergy are :-

Options

A. Immunogens
B. Allergens
C. Antigens
D. Both (1) & (3)

Answer

To answer the question "Agents which cause allergy are:", we need to analyze the options provided and understand the definitions of the terms involved.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the agents that specifically cause allergies. We need to identify the correct term from the options given.

2. **Review the Options**:
- **Immunogens**: These are substances that provoke an immune response. While they can include allergens, not all immunogens cause allergies.
- **Allergens**: These are specific types of immunogens that trigger allergic reactions. They are the correct answer to the question.
- **Antigens**: These are foreign substances that can bind to antibodies or T-cell receptors and induce an immune response. While allergens are a type of antigen, not all antigens cause allergies.
- **Both 1 and 3**: This option suggests that both immunogens and antigens are correct, which is not accurate since not all immunogens or antigens cause allergies.

3. **Identifying the Correct Answer**: Based on the definitions:
- **Allergens** are the agents that specifically cause allergic reactions. Therefore, the correct answer is **allergens**.

4. **Conclusion**: The agents which cause allergy are **allergens**.