Itching due to insect bite is caused by

Itching and stinging pain following an insect bite, particularly from ants or bees, is primarily caused by the injection of formic acid (also known as methanoic acid) into the skin [2]. When an ant bites, it uses its mandibles to grip the skin and injects this acidic liquid, which triggers an inflammatory response characterized by redness, swelling, and irritation [1]. Formic acid is a simple carboxylic acid that derives its name from 'Formica', the Latin word for ant. While other substances like histamine also contribute to the allergic response in humans, formic acid is the chemical agent responsible for the immediate acidic irritation [1]. This effect can be neutralized by applying a mild base, such as moist baking soda, which provides relief by balancing the pH of the affected area [1].

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 2: Exploring Substances: Acidic, Basic, and Neutral > 2.3 Neutralisation in Daily Life > p. 18
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Table 2.3 Some naturally occurring acids > p. 28