Castration play is NOT for everyone and definitely sits at the more extreme end of the fetish scale!  Within the BDSM context, it can be only 'play, but there are masochists who are willing to experience severe body modification processes and have actual medical procedures done to them, in order to live out this fantasy. This involves plenty of risk for the person whose testicles are being restricted, cut, or modified. Castration play is all about intense fantasies and extreme pain. It is NOT for newcomers or beginners and requires precision, expertise, and years of practice. Castration fantasy refers to an erotic fantasy in which the submissive/slave has sexual thoughts and dreams about having their testicles and/or penis removed surgical, often without anesthesia. 

There are medicines that can be prescribed that will assist in reducing libido in men.  It may be an option before embarking on this extreme CBT (cock and ball torture). The most commonly used antiandrogen (a diverse group of medicines used to counteract sexual drive in men), is cyproterone acetate (Androcur), taken orally as a tablet. A true professional Dominatrix will not engage in this sort of play or activity with a newcomer in the BDSM scene and will explain ALL the risks involved. Total castration should not be done without the advice and/or experience of a trained medical professional.