Blonde hair extensions can turn brassy, just like your own blonde hair can start to change colour over time. As our hair extensions are all made of human hair, a chemical process can be triggered and cause the blonde to turn brassy over time, likely due to the chemicals in face creams, sun creams, hard water and even sun exposure. This is natural, and not a fault with the hair extensions themselves. We recommend you try to prevent this by avoiding wearing the extensions when using products that may cause this chemical reaction.