Castor oil has a strong smell primarily due to the presence of ricinoleic acid, which makes up a significant portion of its composition. The unique molecular structure of ricinoleic acid contributes to the distinctive odour. Additionally, trace compounds from the extraction process can further contribute to the scent. Different batches of castor oil may vary in their characteristics, it is worth noting that each batch of castor oil will have its own specific set of characteristics, including its odour. Once the oil come into contact with skin and is opened the smell dissipates. You can use an essential oil of choice also to mask the smell if you are using this for topical use.