The active ingredient in vinegar is acetic acid. This acidic substance gives vinegar its pungent smell.
Acetic acid kills microbes and fungi, which makes vinegar a very effective cleaning agent. This is why many environmentally friendly cleaning products contain vinegar. Acetic acid is also useful for killing mildew and mold, making it a safe alternative to bleach and other harsh chemicals.
Other uses for vinegar include killing weeds, canning and preserving food and adding flavor to pickles. Some pharmaceutical manufacturers use acetic acid to produce medications for treating infections of the external ear canal. The acetic acid clears up this type of infection by killing bacteria or fungi.