The present invention relates to an apparatus for treating skin by means of intense pulsed light (IPL). Such apparatus may be used for the treatment of, for example, cosmetic purposes such as hair depilation or dermatological treatment of skin conditions such as acne or rosacea. The present invention provides an improved apparatus that can be used by a non-medical practitioner and comprises a light source comprising a light emitting element for transmitting light energy to the skin and a charge storage device for discharging an energy dose to the light emitting element. There is further provided at least one sensor for measuring a parameter of the skin and a control system configured to determine the treatment energy dose to be delivered. This treatment energy dose is derived using the sensor measurement and means of reduction in unwanted time delay associated with charging or discharging of the charge storage device in sole dependence on the current or most recently measured skin parameter.