All soap contain alkali which
break up the horny top layer of skin, allowing water to penetrate more (as
well as to escape). Although normal skin renews this horny layer, repeated
use of soap may weaken the repair process. This can cause extreme scaling
and dryness known as chapping.
Perfume added to soap makes it much more appealing to use, but has no other
virtue.... So then?
The safest soap to use is the simplest kind which has no added disinfectant,
and no perfume.
While on the subject, remember that detergents, which are synthetic chemical
compounds, will remove grease from the skin more effectively than soap. But
their actions are too harsh for regular use and they easily cause chapping.