Article by: Perry Romanowski
I’ve just started reading a book called Chemistry Connections and it’s quite good so far. One of the questions had to deal with cosmetics and I thought it was an interesting one to discuss.
Why do cold creams feel cold? And more generally, how do you make a cooling sensation in your cosmetic formulation.
Cold creams are typically Water in Oil emulsions. Classic products like Pond’s Cold Cream is a mixture of Mineral Oil, Water, Beeswax, and Ceresin. It also has a thickener, preservative and fragrance. The product is interesting enough because you don’t see a lot of water in oil emulsions on the market. But what about this cooling sensation?
Physics of cooling
It turns out the cooling effect is not a result of any special chemical, it’s just the water. When the cream is put on the skin, water and the fragrance begin to evaporate immediately. Evaporation is an endothermic process meaning it requires heat to happen. The heat is drawn from the skin which produces the cooling effect. Incidentally, this is the same process the body takes advantage of when you are sweating.
While water in the formula can give you the cooling sensation, there are other compounds which can make a much more intense sensation. Ethanol is great for causing that cooling sensation. Menthol, Methyl Salicylate, Eucalyptus and Tea Tree Oil are other examples of materials that can give a cooling effect. Unfortunately, these can also have unwanted side effects like odor or irritation.