We buy skin care products to either improve our skin or fix a problem. But sometimes there are unintended effects — like acne or rashes. Unfortunately you can't know how your skin will react to a new product until you use it. Luckily, there is a simple rule to follow to help prevent undesirable effects. Getting excited about starting new products as soon as you buy them is normal, however, try to avoid the temptation of applying new products all over your skin. Considering there is no way of knowing how your skin is going to react, only use the new product on a small section of your skin for a few days. If no irritation occurs, you are in the clear to continue using that product. If a rash begins to appear or your skin becomes itchy, you have just saved yourself from an even bigger problem had you applied it entirely to your skin.