It is for this reason that earring posts are commonly made in 14 karat. Rarely do we hear of someone that has an adverse reaction to 18 karat. When you look at making a decision based on wear characteristics alone, there is not enough difference to favor one karat over another. If you view the issue from the standpoint of which will give you the lowest reactivity rate, the 18 karat wins hands down. Each alloy has characteristics that are unique to that alloy.
Gold is alloyed differently for a variety of reasons, including look and price.
In many world cultures, gold jewelry is a symbol of wealth and prominence. In this country, jewelry is viewed in a similar manner. The informed consumer wants to buy the piece that represents the best value and, meets their needs. The most common reason is metallic abrasion, caused by make-up on skin or clothing. Cosmetics often contain certain compounds harder than the jewelry itself, that wear or rub off very tiny particles.