Impermeable dressings considerably increase the absorption of salicylic acid and methyl salicylate. When salicylic compounds are incorporated in bases in which they are but little soluble, absorption is better than with bases in which they dissolve easily. For a given skin surface a maximal amount of ointment exists the increase of which does not increase absorption. In eczema and neurodermitis absorption is greater only when the skin is eroded, whereas in healthy areas or in places which after treatment are nearly back to normal again, the absorption of salicylic acid and salicylates is normal.