The skin is the part of the body which comes into direct contact with the environment and hence it is usually the first part of the body to sustain damage or be exposed to irritant substances. Thus, dermatitis is a fairly common complaint. The symptoms generally begin as itching, sweat retention, increased sensitivity and pain, but lead to swelling, oozing, crusting and scaling, with thickening and hyperpigmentation. Inflammation occurs in response to a number of factors e.g. mechanical, chemical, thermal stimuli, infections or imbalance in the autoregulation processes. All these processes can reduce barrier action and lead to increased permeability of the skin to drugs. Allergic contact dermatitis from drugs is a significant obstacle to the development of transdermal drug delivery systems and various animal models are being investigated to test methods for its prevention23.
Any damaged or diseased area of the skin is likely to display compromised barrier properties and consequently higher drug absorption. Skin permeability is increased in psoriasis and ichthyosis24 25. This is unusual since both of these conditions result in thickening of the stratum corneum, but presumably it does not retain structural integrity.
Irritation and inflammation increase penetration even if the skin layer is unbroken26; ultraviolet light and sunburn also increase permeability. Burning from more conventional sources such as scalding causes greater penetration, the extent increasing with burn temperature but not apparently with burn duration27.
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Do You Suffer From the Itching and Scaling of Psoriasis? Or the Chronic Agony of Psoriatic Arthritis? If so you are not ALONE! A whopping three percent of the world’s populations suffer from either condition! An incredible 56 million working hours are lost every year by psoriasis sufferers according to the National Psoriasis Foundation.