The invention relates to pharmaceutical compositions designed to leave a protective film on the skin, comprising chitosan and agents conferring curative, calming and hydrating properties on irritated skin. The gel is characterised in that it includes between 2 and 8 % chitosan and pre-defined proportions of other components such as between 0.1 and 90 % Portulaca and between 0.1 and 45 % Panthenol, which confer improved therapeutic characteristics on the product, and other components which provide the gel with particular characteristics and render same suitably stable over a prolonged period of time. Said gel is applied externally and is suitable for use on irritated skin, superficial bums, dermabrasions, post-dermabrasion, post-laser treatment and on eroded skin in general.