Using a skin product for the first time is tricky, because you never know what effect the chemicals in the product will have on your skin. So, in order to avoid a major complication, it is suggested that you patch test - take only a small quantity of the product and apply it either on the inside of your wrist or your elbow. Make sure you rub the product into your skin properly.
Leave the area and allow the product to settle on the skin. This could take anything from a few hours to a day, so be patient and do not jump to conclusions or decide on a result before 24 hours have elapsed.
You cannot wash your skin during this time, so try to stay away from showers and washing your hands.
During these 24 hours, you need to constantly check for any signs of swelling, burning or redness.
If you find that you are experiencing these symptoms, do not panic, and gently rub the product off with water. Then, dry the area which was used for the experiment.
After the 24 hours are complete, check for signs of a negative reaction. If the skin is perfectly fine, then you can conclude that the product in question is safe for your body and face.