Abstract: The present invention relates to a hairbrush with a plurality of filaments which is formulated by a mixture of thermo-sensitive color-changing powder and plastic materials, and the color of which varies with temperature, and the method of manufacturing such thermochromic filaments. The hairbrush comprises a handle, a head which has a number of pre-set filament holes on its surface and is attached to the handle by any convenient means, and a plurality of filaments which is formulated by extrusion process from plastic material of 98% to 94% by weight plus a mixture of 2% to 6% by weight comprising melamine plastics of 6%, latent dye of 4.5%, fixing agent of 10%, fatty acid of 0.5% and metallic oxide of 79% by weight and is attached to the filament holes by any convenient means.