Human hair extensions have more free electrons with a negative charge than protons which have a positive charge on their surface. It is also well-known that like charges repel and unlike charges attract. These twin bits of knowledge help in selecting the various hair care products used in the maintenance of human hair extensions. It is obvious from the above that hair care products which need to remain in the hair for a longer period need to be positively charged so that they may be attracted and retained by the negatively charged human hair extensions. Similarly, those that have to be rinsed out should be negatively charged so that they can be repelled and removed easily. Shampoos for human hair extensions should be negatively charged so that they perform their function and then can be easily washed out. Conditioners and moisturizers need to stay longer in the hair and should therefore be positively charged, such that they are retained and continue to perform their function effectively. Apart from this, another impact of this interaction between the positive and negative charges is the surface energy of the human hair extensions. The surface energy influences the luster, health and longevity of human hair extensions.