What kind of skin lesion is a pustule?

A pustule is a small, raised skin lesion filled with pus, which is a yellowish-white fluid consisting of dead white blood cells, bacteria, and cell debris. Pustules are typically caused by bacterial infections of the skin, such as impetigo, folliculitis, or acne. They can also be caused by viral infections, such as chickenpox or shingles. Pustules may also occur as a result of allergic reactions or certain skin conditions, such as eczema or psoriasis.