The interferons are a group of naturally occuring biologic response modifiers, many of which now are available commercially for therapeutic purposes. These agents have antiviral properties, although they also exhibit antiproliferative, immune-enhancing, and differentiating effects. The release of natural agents that could treat infections and cancer was intriguing, and the potential uses were exciting. The interferons proved to exert effects in several skin diseases but not to be first-line therapy in any of these.

There are three main types of interferons; ⍺ and β interferons (collectively referred to as type 1), which are similar structurally and exert common effects, and γ interferon (type 2 interferon), which is dissimilar chemically and functionally to the others. Almost any cell can produce interferon-⍺ or interferon-β in response to an appropriate stimulus, especially a virus or cytokines. Interferon-γ can be produced only by stimulated T lymphocytes and natural killer cells.