Oils with a high share of polyunsaturated fats are more prone to oxidation than oils that are mostly monounsaturated or saturated. Oxidation happens when the oil is exposed to light, heat, or air, and it changes the taste and smell. The main storage rules are simple: keep the bottle in a cool, dark place — a kitchen cabinet away from the stove works well — close the cap tightly after each use, and do not leave it in direct sunlight.
Because the bottle is 100 ml, it is a small amount. If you use it regularly, it will be finished within a few weeks, which is good because the oil is best fresh. To check if it is still good, smell it and taste a tiny drop. Fresh rosehip oil has a smooth, slightly fruity aroma. If it smells sharp, bitter, or like paint, or if the taste is strongly bitter, the oil has oxidized and is better not to use it.
Check the best-before date on the label and follow it. There is no need to refrigerate it, but if your kitchen is warm, a fridge is a safe option — the oil may become thick when chilled, which is normal, and it returns to a clear liquid at room temperature.