Hairdressing appliance comprising - a portable treatment unit configured at least to spray steam on the hair, the portable treatment unit comprising two arms (5, 6) configured to form a clamp provided with two hair treatment surfaces (8, 9) arranged opposite each other in order to clamp a lock of hair between them, the first arm comprising a vaporisation chamber and first spraying means (12, 12') configured to be connected to the vaporisation chamber and to spray steam towards the outside near the treatment surface of the first arm - a steam transfer system (15, 22) configured to move steam from said first arm to the second arm and inversely to spray this steam towards the outside on the side of the inner face of the second arm, near the treatment surface of the second arm, - the transfer system comprising at least one duct configured to transfer steam from the vaporisation chamber to the second arm and second spraying means configured on the second arm to be connected to the duct and to spray steam towards the outside near the treatment surface of said second arm, - wherein the duct comprises a first duct portion configured on the first arm to be connected to the vaporisation chamber and a second duct portion configured on the second arm to be connected to the second spraying means, said first and second duct portions being configured to communicate with each other when closing the clamp and form said duct, wherein the first duct portion comprises a male end and the second duct portion comprises a female end, said male and female ends being configured to fit into each other when closing the clamp. - a portable treatment unit configured at least to spray steam on the hair, the portable treatment unit comprising two arms (5, 6) configured to form a clamp provided with two hair treatment surfaces (8, 9) arranged opposite each other in order to clamp a lock of hair between them, the first arm comprising a vaporisation chamber and first spraying means (12, 12') configured to be connected to the vaporisation chamber and to spray steam towards the outside near the treatment surface of the first arm - a steam transfer system (15, 22) configured to move steam from said first arm to the second arm and inversely to spray this steam towards the outside on the side of the inner face of the second arm, near the treatment surface of the second arm, - the transfer system comprising at least one duct configured to transfer steam from the vaporisation chamber to the second arm and second spraying means configured on the second arm to be connected to the duct and to spray steam towards the outside near the treatment surface of said second arm, - wherein the duct comprises a first duct portion configured on the first arm to be connected to the vaporisation chamber and a second duct portion configured on the second arm to be connected to the second spraying means, said first and second duct portions being configured to communicate with each other when closing the clamp and form said duct, wherein the first duct portion comprises a male end and the second duct portion comprises a female end, said male and female ends being configured to fit into each other when closing the clamp.