Immediately after applying leather conditioner to my semi-aniline leather sofa, there was a musty odor that smelled sky high. It stank like I just got my expensive sofa from a rented storage room after 10 years. My sofa was bought new from an expensive furniture store and has never seen a warehouse or even a basement. Some kind of chemical reaction took place immediately, causing the most horrible musty smell anyone knows. It even stuck to my clothes. I had to spend over 4 hours removing the air conditioner and deodorizing the entire sofa.