About UV Sensor Technology    

The basic principle that underpins the UV Sensor Technology used in sunscreen monitoring stickers, regardless of the product/brand, is that a reversible colour changing UV photochromic pigment is used in producing the circular UV sensor on every UV Alert Patch. This highly specialised, patented pigment reacts only to ultraviolet rays (UVR) within the 285 to 395 nanometer (nm) range (UVA and UVB) and does not react to visible light (between 400 – 700nm) or Infrared light (>700nm). Therefore, the UV pigment only changes colour in the presence of UVA and UVB (the two harmful areas of the sun’s spectrum which are responsible for skin cancer and skin aging, with UVB also being also responsible for sunburn). The reversible colour changing process (clear/pink to purple and back to clear/pink when sunscreen is applied or reapplied) can occur over and over (thousands of times), so the UV pigment used in producing UV Alert Patches lasts a very long time.

Sunscreen blocks UV, preventing it from making contact with the skin. By applying sunscreen over UV pigment, this prevents most of the suns UV rays making contact with the pigment (e.g. an SPF 50 sunscreen blocks about 98% of UV). As a result, the pigment remains clear to pink. However, as the sunscreen loses its protection more UV makes contact with the pigment, resulting in the pigment turning from a clear to pink to purple in colour.