A UV radiation (UVR) response indicator comprises a first UVB and/or UVA radiation sensitive material which has been modified so as to display an altered characteristic in a delayed manner in response to UVB and/or UVA radiation exposure. The UV indicator is capable of displaying exposure to increased UV radiation over a period of time. The present invention also relates to a method of displaying a relative amount of exposure to UVR by a UV indicator over a period of time. The invention is particularly useful in detecting the level of exposure to sunlight or sunbed radiation.