The simple answer is use of chemicals, heat and lack of moisture. We eat food to feed our bodies with nutrients which eventually makes their way through our system to feed our skin and hair. We cannot feed hair extensions in the same way so we need to use alternative methods.
Use organic and no sulfate shampoo's to regularly feed, moisturise and treat your hair extensions. Remember, coloured hair goes through a chemical process, especially when lightened to blondes and special colours, this is unavoidable to achieve the colours we all desire.
A little moisturising oil (we prefer Almond) each week is key.
Avoid shampoo and conditioning products which use Sulfates, Isopropyl Alcohol, Formaldehyde and Propylene Glycol, these are strong chemicals which will strip the hair of natural oils and leave them dry and sometimes damaged if used for a prolonged period of time.