Hirudine is the first natural anti-coagulant ever described. It is used for its anti-coagulant properties in plastic surgery or for the treatment of post-phlebitic diseases. Natural hirudine is extracted from the saliva of the Hirudo medicinalis leech, but it can also be found in crushed leech and included in a cream (Hirucrème). Side effects to hirudine are considered to be rare.We report a contact eczema caused by an extract from the medicinal Hirudo medicinalis leech. This was confirmed by the patch tests. However, we noticed a negativity of these tests with two analogs of the recombinant hirudine.Several cases of contact dermatitis with Hirucreme have been described. The analogs of recombinant hirudine, which share similar biological activity, have a very close molecular structure. They are indicated via the systemic route for thrombopenia related to heparin for the prevention of severe thromboses. The negative patch tests does not allow definite conclusion, but they prove that these molecules do not always lead to cross-allergies.