Ointments, creams, and lotions: butter, mayonnaise, and milk.

What is the analogy, or what do all of these have in common?

Physically, they're all the same. They're emulsions of oily components and watery components.

The difference between an ointment and a cream, or butter and mayonnaise, is the proportion of oil and water. More oil, thicker, more water, thinner, and likewise with a lotion and milk.

So, why have the different thicknesses? What is the purpose of a cream versus an ointment (or salve)? That's a good question. It's easy to answer the question in food, it's a matter of taste. And, mostly the same for ointments, creams, and lotions. Also mostly a matter of taste, with some qualifications which I describe below.

In older days, it seems heavier creams and ointments were more favored. When is the last time you heard anyone refer to a salve, by the way? In the last 30 years, there has been a fashion for lower oil content emulsions, more watery feeling preparations, and a lot of marketing against "oily" products. It is mostly fashion, with only one real difference, which is the ease with which you can put smaller and smaller amounts of oil on your skin.

The water does nothing but evaporate and also provide an environment for lifeforms like molds, fungi, yeasts, and bacteria. Maybe that wouldn't have been wise in the old days when a skin preparation needed to be stored without many chemical preservatives. As for what the skin needs, that is clearly oil, since the water has nowhere to go and nothing to do, except shrivel your skin over long times.

Since a cream is an oil and water mixture, where globules of oil are suspended in water (in an oil in water emulsion, as opposed to a water in oil emulsion, in which the water is present as globules in an oil base - think butter versus milk), something has to be there to make it stable, so it doesn't separate like a badly made sauce. That is the emulsifying agent. In the case of mayonnaise, it is the lecithin present in the egg yolk. In creams, many are used, almost all synthetic: polysorbates and cetearyl alcohols are two examples, and they are also either the same or similar to many detergent compounds.

If you didn't have the emulsifier, the cream would separate into oil and water. When you place this on your skin, the oil droplets (in the case of a typical lotion or cream) spread out on your skin in the water matrix, the water evaporates, and what you're left with is the oily part on your skin, since the oily part won't evaporate as easily.

In other words, every lotion, cream, or ointment is really only distributing oil to your skin, and not much more. This is assuming there aren't harsher ingredients like alcohols or soaps that are dissolving or stripping away the lipids on top of your skin, and a part of your skin (the topmost layer, the stratum corneum).

In today's cosmetics science, many more ingredients are added since you want the cream to feel good: smooth, luxurious, smell good, and have a nice color, and not change.

When the water is added, now also the molds, fungi, bacteria, and other living things must also be kept at bay, meaning anti-microbials (which in Europe are called preservatives). You must have what Americans call preservatives too, which are known as antioxidants in Europe, to preserve the oily component. These are typically BHA and/or BHT.

So, maybe you have noticed something by this point, which is kind of like a question in logic: If the only thing that is happening is the laying down of a layer of oil on your skin, whether it's an ointment, cream or lotion, why go through all the trouble of making the ointment, cream or lotion in the first place?

That is a good question. How and why did we get to this point where all those added things are in there? I'm not sure there is a real exact answer, but it's more of a history question. My best guess is that in the 50's and 60's when polymers (plastics) like silicone came into existence, technology was absolutely the best selling point for any product (remember how everything was space age?) and polymers provided many opportunities to improve properties which cosmetics chemists had probably long sought after, smoother, more luxurious creams, etc. From the standpoint of stability and feel, I have no doubt that today's creams are far superior to the those of the 40's, which were mostly cold-cream like and that was it.

And, I think someone just started the marketing snowball of oil = bad, watery = good, and it became technologically challenging for everyone to make a better cream. Gels, etc. then came along as well.

I think it was all pretty much technology push - new materials gave new feel possibilities, and it was a way to improve upon the competition, and then everyone gets into a race. In other words, Marketing driven.

The idea of a salve-like substance that lasts and provids a layer that doesn't absorb much or rub off easily makes sense. It's good for continued protection, delivery of an ingredient, etc. for different situations, like serious wounds, burns, etc. In that case, the skin may not have enough of it's own protective barrier against moisture loss. So, oil versus vaseline-like substance makes a lot of sense for different situations. It's the part where one adds water which really is just unnecessary to the task at hand and introduces a lot of complication....

So, why go through all of the trouble, and also put another dozen substances on your skin if what you really want is to deliver a little oil?

So, why do you want to deliver a little oil for that matter? That's the subject for the next post.