Corticosteroids are better absorbed and more permeable in regions of thin epidermis, such as the eyelid, gonads compared to thicker regions of epidermis, such as the sole. In fact, the penetration difference may be by 300-fold. Diseased skin such as inflammation and desquamation can increase absorption by tenfold.
High-potency steroids are used for thicker regions of the skin (eg palms and soles) and in nonfacial/nonintertriginous areas for severe skin infections.
Medium- to high-potency steroids are useful for regions of thin epidermis and areas of occlusion, such as the eyelid and axilla, respectively, whereas low strength preparations should be used for large surface areas.
The amount of steroid may determine the risk for adverse effects. One fingertip unit (FTU) is equal to 0.5 grams. The suggested dose of FTU is dependent upon the body region being treated. Topical corticosteroids are recommended for once to twice daily use (there is limited beneficial evidence to applying topical corticosteroid more than once per day.
To avoid misuse of topical steroids and the consequent adverse events, a health practitioner needs to be aware of which skin conditions are responsive. But more importantly, which class is effective foe what skin condition.
