It can happen that, for various reasons, leather is impregnated with a strong smell, which can either be of origin and depend on the characteristics of the type of leather skin used or the treatment it received during the tanning process, or acquired after an incident (contact with animal urine for example).
We recommend to proceed in two steps:
1- Cleaning-Disinfection : to begin with, is is important to clean the leather in depth with Cleaning Regenerating Soap. Continue with Leather Cleaner Renomat to disinfect your leather and eliminate possible fungus.  
2- Regular care : Afterwards, regular care will make the smell fade away for good. Use different products according to the object to be treated:
For fine leather goods or leather clothes, use  RENOVATOR Polish Saphir Médaille d'Or.  This very rich product perfectly nourishes the leather, and its wax components (beeswax, mink oil for example) will leave a pleasant typical smell.
For leather furniture (sofa, armchair etc.), choose Cream Renovator Avel because it contains the greatest amount of waxes and perfumes. It will perfectly renovate your leather and leave a very pleasent scent.