Immune System

The ELISA (Enzyme-Linked Immunosorbent Assay) method works on the principle of antigen-antibody interactions. In this method, an antigen is attached to a surface, and a specific antibody is used to bind to the antigen. The antibody is linked to an enzyme, and the enzyme reacts with a substrate to produce a detectable signal, often in the form of color change, indicating the presence of the antigen.

Step 1: Understanding the Question.
This question asks about the chemical responsible for causing allergic reactions in the body.

Step 2: Analyzing the Options.
(A) Anti-histamine: Anti-histamines are used to treat allergies, but they are not responsible for causing them.
(B) Histamine: Correct — Histamine is the chemical released during an allergic reaction, causing symptoms like itching, swelling, and inflammation.
(C) Arsenic: This is a toxic substance, but it is not the cause of allergies.
(D) Bees: While bee stings can trigger allergic reactions, bees themselves are not a chemical.

Step 3: Conclusion.
The correct answer is (B) Histamine, as it is the chemical responsible for causing allergies.