Thirty preparations of topical corticosteroids are included in this appraisal (see appendix D). Topical corticosteroids are classified according to their potency. This is determined by the amount of vasoconstriction a topical corticosteroid produces and the degree to which it inhibits inflammation (a more potent product increases suppression to the inflammatory pathway). In the UK, 4 potencies are recognised: mild, moderately potent, potent and very potent. Across the different potencies, products have different formulations and different strengths (for example, 0.025%, 0.1%, 0.5%) and are available in various preparations (for example, ointment, cream, lotion, foam).