A peptide is a short chain of linked amino acids that act as small proteins, dictating the behavior of other cells and molecules in the body. There are more than 7,000 known peptides in the human body. Peptides are useful in treating various conditions as they can influence the behavior of cells. Clinical use of peptides is considered safe, and there are now many FDA-approved medications containing peptides available. Peptide therapy is typically administered via injection, skin creams, nasal sprays, or in pill form.