The invention relates to a pharmaceutical composition consisting of snail slime of Helix aspersa muller (Cryptophalus aspersus) (5% to 50%), chamomile extract (5% to 10%), honey (5% to 10%), and additives and / or pharmaceutically accepted excipients to form a formulation having low, intermediate or high viscosity (1 to 1000 Pa-s). By dipping a patch or bandage of gauzy fabric into the composition in the form of a lotion, shampoo, soap, cream or gel, the composition is applied on lesions caused by psoriasis. The composition can also contain natural extracts, such as marigold extract, propolis, and vegetable oils. The invention also claims a method for obtaining the composition and the use thereof to prepare a drug or device for preventing, treating or curing psoriasis lesions on the head, the skin of the body or of the face.