Our Flexalite bristles, are capable of resisting heat up to 220°F (104°C). All our brushes, including all the components are “heat resistant” but not heatproof… similar for clarification of a watch that’s “water resistant” but not “waterproof”.The Knot Dr brush is designed for detangling but if you choose to use The Knot Dr brush with a hairdryer we recommend when blow drying keeping a minimum of 4” (10 cm) distance from the bristles, as getting too close with extreme heat is not only damaging for your hair but over a period of time it will damage and deform the bristles, shortening the life span of your brush.