Lanolin

Lanolin is an emollient, very thick substance (essentially a wax) that is extracted from sheep's wool. It has long been burdened with a reputation for being a sensitizing agent, which has always been a disappointment to formulators because lanolin is such an effective moisturizing ingredient. A study in the British Journal of Dermatology concluded "that lanolin sensitization has remained at a relatively low and constant rate even in a high-risk population." Based on a review of 24,449 patients who were tested with varying forms of lanolin, it turned out that "The mean annual rate of sensitivity was 1.7% - and it was lower than that for a 50% concentration of lanolin. The amounts of lanolin used in products like facial and body moisturizers are much less than this, so the risk, if any, is negligible.

Lanolin is a very good ingredient for someone with dry skin, though it can be a problem for someone with oily or breakout-prone skin. Also, as an animal-derived ingredient, lanolin is sometimes viewed as less favorable in comparison to synthetic or plant-derived alternatives.