SUMMARY Steatorrhoea has been found in a large proportion of patients with inflammatory dermatoses, especially eczema and psoriasis. It is due to the rash itself and disappears rapidly after topical treatment of the skin. This particular enteropathy, unlike that associated with dermatitis herpetiformis, is not accompanied by an alteration in the stereomicroscopic appearance of the small bowel mucosa. The mechanism is not known. It is important to differentiate dermatogenic enteropathy from gluten sensitivity which has produced a rash, as in the former condition a gluten-free diet is not indicated.Dermatogenic enteropathy is an entity which is best understood in the context of the four known associations between skin and gut abnormalities (Shuster, 1967a and b;Shuster and Marks, 1970). These are: when malabsorption causes a rash, as in tropical sprue and 'idiopathic' steatorrhoea (group I); when skin disease causes malabsorption (dermatogenic enteropathy (group II); when skin and gut lesions are both due to the same pathological process as in the collagenoses (group III); and (group IV) when skin and gut lesions are indirectly related, as in dermatitis herpetiformis, which is associated with the coeliac syndrome more often than would be expected by chance but not in any of the three previous instances.It can be seen that dermatogenic enteropathy differs fundamentally from other forms of malabsorption associated with skin disease in that it is caused by the rash itself, and some of the evidence for this has been presented and discussed already Shuster, 1967a and b;Marks, 1968;Shuster, 1968a and b;Marks, Shuster, and Watson, 1970;Shuster and Marks, 1970). As new information has become available it has supported the authors' original hypothesis and only in one respect is there an apparent conflict between the present paper and a previous report (Shuster, Watson, and Marks, 1967b). The present authors no longer believe that there is evidence of a structural mucosal abnormality in dermatogenic enteropathy. This paper will be concerned mainly with malabsorption of fat, although there is evidence of malabsorption of D-xylose (Marks, 1968;Shuster and Marks, 1970) and iron (Marks and Shuster, 1968) and perhaps folate (Kaimis, Summerly, and Giles, personal communication, 1969) and vitamin B12 in some patients with dermatogenic enteropathy.The interpretation of results of many 'absorption' tests in patients with skin disease is notoriously difficult (Knowles, Shuster, and Wells, 1963;Fry, Shuster, and McMinn, 1965;Doran, Everett, and Welsh, 1966; Shuster, 1967a and b;Marks and Shuster, 1968;Shuster and Marks, 1970) and will be discussed only briefly.