Peptides are molecules made up of two or more amino acids. The number of amino acids that make up the peptide dictates whether it is called a dipeptide (two peptides), a tripeptide (three peptides), a tetrapeptide (four peptides) and so on. There are several different types of peptides being developed or already in use for a wide range of dermatologic applications. For example, signal peptides, which are thought to initiate wound healing and increased collagen production, are currently used in several over-the-counter anti-aging and anti-wrinkle skin care products. Carrier peptides literally “carry” trace elements like copper throughout the body, and are essential for wound healing of the skin. One carrier peptide, called glycyl-l-histidyl- l-lysine (GHK), has several important cellular actions and is thought to improve fine lines, hyperpigmentation and skin texture, in addition to aiding in wound healing. Neurotransmitter-inhibiting peptides are used in topical cosmeceutical formulations because they have a similar effect to botulinum-neurotoxin. The most popular cosmeceutical neurotransmitter-inhibiting peptide is acetyl hexapeptide-3, marketed as Argireline®.