Papule

A papule is a small, solid and usually conical elevation of the skin. Papules do not contain pus, which distinguishes them from pustules. Papules often occur in clusters and can accompany rashes.

A condition that causes a papule is called a "Papulosis". Examples of papuloses include:
 * Lymphomatoid papulosis
 * Bowenoid papulosis
 * Clear cell papulosis

Causes
Papules can be caused by:
 * Inflammation (which in turn is often caused by infection or abrasion of the skin)
 * Accumulated secretion of skin tissue (hyperplasia) or glandular fluids.
 * Presence of an infection such as disseminated histoplasmosis.
 * Hypertrophy of skin cells
 * Acne