Is it safe to use castor oil on varicose veins while pregnant?

Yes but doesn't help: Castor oil doesn't do anything for varicose veins. Also, it smells funny. Compression stockings are a good way to shrink the veins during pregnancy; if they don't go away, then other options can be considered.

Yes but why : Castor oil will not hurt varicose veins. I am not sure it will help either apart from keeping them moisturized.

Castor oil and veins: Applying castor oil topically to varicose veins whether pregnant or not will not help the varicose veins. If you have a varicose vein problem then you should see a vein specialist. A moisturizing cream such as aloe will help the texture of the skin overlying the veins.