ABSTRACT
The use of transdermal drug delivery systems (TDDS) is widely recognized (1).
In 2004, the U.S. market for these patches exceeded $3 billion annually (2).
The advantages and disadvantages of transdermal drug delivery are well-known
(3,4) and the disadvantages include the potential for contact dermatitis [CD, allergic
and irritant contact dermatitis (ACD and ICD)]. Contact urticaria, photoirritation,
and photoallergic contact dermatitis are possible but have not yet been identified as
a clinical problem. CD literally means “inflammation of the skin” when exposed to
certain substances and there are two main types: ACD and ICD (5). Table 1 shows
the clinical and histopathological features of ACD and ICD (6). It is evident that
there are similarities but, apart from the histological features, the distribution of
lesions is widespread for ACD and mostly localized for ICD, and the course of
healing, i.e., crescendo phenomenon for ACD and decrescendo phenomenon for
ICD are the characteristics that help distinguish one from the other (6).
