Histamine is a chemical produced by the body that plays a crucial role in the immune response. It is released during allergic reactions and helps to regulate various physiological functions, including stomach acid production and neurotransmission. When the body encounters an allergen, histamine is released from certain cells, leading to symptoms like itching, swelling, and redness. In addition to its role in allergies, histamine is involved in the sleep-wake cycle and can affect mood and cognition. It is also found in certain foods and can cause reactions in sensitive individuals. Understanding histamine is important for managing allergies and related conditions.