iS Clinical products containing Vitamin C may occasionally fizz or bubble when opened. This results from shaking, and pressure changes experienced by the product during shipping, and does not affect product efficacy. We recommend that, on first opening the product, the cap be turned one-quarter turn to break the seal and then allowed to rest for approximately thirty seconds. The cap should continue to be turned one-quarter turn at intervals of several seconds until the container has been fully opened. These products should be stored at room temperature or below but not at freezing temperatures and not in direct sunlight.