Ultraviolet (UV) rays found in UV Sterilizers accelerate the deterioration of Silicone Nipple, resulting in the degrading of silicone material and lead to hardening of silicone material which may cause crack and tear on products. Plastic parts such as bottles and bottle caps may also deteriorate due to UV rays. Hence, we do not recommend UV Sterilization to be used for PIGEON Products made of plastic and silicone material such as our Nursing Bottles & Nipples.