Faced with the failures he encountered in the treatment of chronic diseases, using only the principle of similarity, Samuel Hahnemann gradually developed a more global approach to the patient. He identified three miasms, nowadays also called chronic reaction modes (CRM), corresponding to the different reactions of the body to the disease. Taking scabies as a model, he developed the psoric miasm; based on urethral infections and venereal warts, the sycotic miasm and on syphilis, the syphilitic miasm.

To provide diagnostic information in order to identify a patient's CRM so as to propose the most effective therapeutic strategy.

By comparing our clinical experience with Hahnemann's writings, we propose the essential characteristics of each CRM, using dermatology to illustrate the point.

Psora is by far the most frequent CRM. It corresponds to a centrifugal struggle of the body against the disease. A balanced psora means being in good health. It covers many dermatoses, allergies and common functional pathologies when it is out of balance.

The real genius and originality of Hahnemann's work lies in the discovery of CRM. It thus provides us with a wonderful means of further individualisation. However, a chronic pathology almost never corresponds to a pure CRM. It is usually the combination of two or even three CRMs often requiring multi-diathetic treatment.