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The correct answer focuses on the role of histamine, which is a chemical released by the immune system during an allergic reaction. When the body encounters allergens—substances that are typically harmless but provoke an immune response—histamine is released in excess. This overabundance of histamine leads to various allergic symptoms, such as headaches, rashes, and sneezing, as it affects blood vessels and nerve endings. The presence of these symptoms indicates that the body is reacting to the allergens, and histamine plays a central role in mediating these reactions.

The other options, while related to the immune response, do not specifically identify the mechanism that causes the acute symptoms associated with allergies. Antibodies are produced in response to allergens, but they don't lead directly to the symptomatology discussed. Malfunctioning of the immune system might imply an inaccurate response, but it doesn’t directly highlight histamine’s role in causing the symptoms. Lastly, the attack by harmless substances is too broad and does not explain how histamine causes the resulting symptoms.