Real Human Hair Extensions can be heat styled at any temperature that you would use on your own hair (see exception for light blondes below). They are not synthetic and will not melt, but high temperatures can cause colour fading in the same way that your own hair colour fades with heat.
Exception for Light Blondes
All our hair extensions are made from naturally black to dark brown hair and due to the salts and catalysts used during bleaching to reach the lightest blonde colours, high styling temperatures can cause a burnt orange discolouration on blondes. This is extremely difficult to remove when caused by heat often requiring several bleach and toning treatments. To minimize the chance of this happening, temperatures below 160c should be used on blondes and heat protection products are to be considered essential.