Allergens are

Options

A. certain microbes which are pathogenic
B. weak antibodies produced by certain substances in the body
C. antigens which produce sensitive reactions in the body
D. none of these

Answer

To answer the question "Allergens are," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Allergens**:
- Allergens are substances that trigger allergic reactions in individuals. They are not pathogens or microbes but rather specific substances that the immune system mistakenly identifies as harmful.

2. **Definition of Allergies**:
- Allergies are exaggerated immune responses to these allergens. The immune system reacts strongly to what it perceives as foreign invaders, even when they are harmless.

3. **Role of Antigens**:
- The substances that cause these allergic reactions are known as antigens. When allergens enter the body, they can provoke an immune response, leading to symptoms of an allergy.

4. **Histamine Release**:
- Upon encountering an allergen, the immune system activates mast cells in connective tissues, which release histamine. Histamine is responsible for the symptoms associated with allergies, such as swelling and inflammation.

5. **Identifying the Correct Option**:
- Given the options provided:
- Certain microbes which are pathogenic
- Weak antibodies produced by certain substances in the body
- Antigens which produce sensitive reactions in the body
- None of these
- The correct answer is that allergens are "antigens which produce sensitive reactions in the body."

### Conclusion:
The answer to the question "Allergens are" is **option 3: antigens which produce sensitive reactions in the body**.

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