Somewhat paradoxically, the treatment given by physicians to their acne patients may occasionally aggravate the problem. For instance,  longterm treatment with oral antibiotics, especially tetracyclines, may produce an untoward change in the skin  microbiological flora. In particular, it may permit an increase in the number of Gram-negative organisms, especially Proteus species or Enterobacter-Klebsiella species.53 (These organisms can be isolated from the lesions and from the nostrils.) This may result in the development of further superficial pustules or cysts. An  increase in the number of Pityrosporum ovale (Malassezia furfur) is also claimed to be responsible for  follicular  pustular acne associated with longterm treatment with tetracycline.

Even time-honoured,  but  not necessarily proven, acne therapy may also aggravate acne. Topical sulphur preparations have been  used for  many  years  in  the treatment of acne. Mills and Kligman suggested that sulphur may aggravate the situation by encouraging the development of closed comedones. Strauss et al  denied this link.56 the acne lesions. No information was given as to how long, if at all, the lesions took to resolve. Another study reported that  two patients developed  a  severe  dense eruption of open comedones, closed comedones and follicular cysts after deep cobalt therapy.58 Although the lesions may be a product of follicular hypercornification, the dermis may be playing a role, as evidenced by  the degenerative dermal changes that  are always present in this group of patients. In a way, therefore, this type of acne is similar, regarding genesis, to  senile comedones.