Fragrance is the most common cause of allergic skin reactions to cosmetics. While the terms "unscented" and "fragrance-free" are used somewhat interchangeably, they are not precisely the same. "Unscented" generally means that the manufacturer has not added a specific fragrance to the product. "Fragrance-free" implies that the product has no odor. However, even if the product has no scent or odor, it may contain masking fragrances that serve to block the odor of other ingredients.