Body milk vs body lotion: the difference, and which to choose

The two best-known examples of what chemists call an emulsion are in every fridge. Milk is milk fat broken into tiny droplets that float in water. Butter runs the other way: droplets of water held inside fat.

Body care borrowed both names from the kitchen, and it had good reason to. Body milk and body butter sit at opposite ends of the same scale. At one end is a texture with a great deal of water, which spreads easily and disappears into the skin. At the other is a texture with a great deal of fat, which stays on the skin and looks after it for longer. Lotion sits right beside milk, and cream somewhere in the middle.

Once you understand the scale, you can read any bottle on the shelf.

Water, oil and what holds them together

Lotions, creams and most body milks are made of two parts that would otherwise refuse to mix: a water phase and an oil phase. A third ingredient, the emulsifier, keeps them together so they do not separate in the bottle.

When the oil is broken into droplets inside the water, the result is an oil-in-water emulsion. It is less greasy and rinses off with plain water. When droplets of water are broken up inside the oil, the result is the reverse, a water-in-oil emulsion. It is greasier, leaves an oily layer on the skin and does more to slow the loss of water. Most lotions on sale are the first kind.

The basin will tell you which one you have. If your hands come clean under water alone after applying it, you were holding an oil-in-water emulsion. If a slippery film stays behind, you were holding something with a good deal more fat. The kitchen again: a milk glass rinses clean, a butter knife does not.

This is also why lotion is as white as milk. The tiny droplets scatter light of every colour equally, and the eye reads that as white.

Body milk vs body lotion: your arm has the answer

Pharmaceutical scientists who set out to classify skin preparations properly ran into a problem familiar to anyone who has stood in front of a shelf. Lotion, cream, gel and ointment do not mean the same thing in every book. The meaning depends on the source, on the market and on how a word happened to settle into use. If experts in medicines struggle to agree on these words, you are entitled to be confused in a shop.

Their conclusion was a simple one. The property that best separates a cream from a lotion is how thick it is and how it flows.

Body milk is a trade name for a white, oil-in-water emulsion. There is no settled rule that makes a milk always thinner than a lotion, or the other way round. Which of the two is thinner is up to whoever made it.

So the best test is your own arm. Squeeze a little onto the inside of your forearm and watch for three things: how it spreads, how quickly it disappears and how the skin feels a little later. Those three answers tell you more than the word on the label.

The scale, from thinnest to thickest

• Milk and lotion. The most water and the thinnest texture. They spread most easily and absorb fastest.
• Cream. More oil and less water, so it is thicker and heavier. It absorbs more slowly, but you do not need to apply it as often.
• Body butter. The rich end of the scale: thick, with a large share of fats such as shea butter.
• Pharmacy ointment. The best at holding moisture in the skin, and the greasiest of them all.
• Oil. It stands apart. There is no water in it at all, only fat that is liquid at room temperature.

Three jobs in every bottle

Three jobs go on inside the bottle, and each texture mixes them in its own proportions.

• Humectants attract water and hold it in the outer layer of the skin. The best known are glycerin and urea.
• Emollients soften and smooth the skin by filling the tiny cracks in its outermost layer. Plant oils and butters belong here.
• Occlusives form a thin protective layer that slows water evaporating from the skin.

A thin texture leans mostly on water and humectants, so it sinks in quickly. The greasier the texture, the thicker the layer it leaves on the skin.

On the label you can recognise them by name. Aqua is water. Glycerin and Urea are humectants. Anything with Oil or Butter in its name, such as Argania Spinosa Kernel Oil or Butyrospermum Parkii (Shea) Butter, is an emollient.

In practice: when the label is full of names ending in Oil and Butter, expect a richer texture. When the water comes with glycerin and a few light emollients, expect something that disappears into the skin quickly.

Which texture, and when

• Slightly dry skin. A light milk or lotion, for some people only once a day, in the evening.
• A hot day, or a morning before work. A texture that disappears fast, so you can dress and leave straight away.
• Dry skin and the cold months. A thicker texture. A cream gives skin more moisture and holds on to it better than a thin lotion, and a humidifier helps, keeping the air in the room above 30 per cent humidity.
• Skin that is always dry, in the evening. Body butter or ointment. They sit at the greasiest end of the scale, so they are easiest to wear when you are not going anywhere.

The scale moves with the seasons. The same skin can ask for a milk in July and something thicker in January.

After the shower

Every one of these textures has the same best moment: as soon as you step out of the shower. Applied then, it holds water in the skin and stops it evaporating. The same product applied much later does less.

If you wash with a glycerin body wash, the wash and the milk work together: the glycerin from the wash binds water, and the oils in the milk keep it on the skin. If you use a scrub as well, it goes between the wash and the milk, and the whole routine is set out step by step in our guide to body care after the shower.

Where ANU sits on the scale

ANU does not pour; the bottle needs a light squeeze. That puts it at the thick end of the milks, right next to cream, and yet it disappears into the skin in a few seconds.

Water is the first ingredient. With it come glycerin, which binds water, two emollients that make it spread beautifully, and argan oil and shea butter, which soften the skin. Fittingly, ANU means a well: a source of moisture for the skin whenever you need it.

It goes on right after the shower, on dry skin or skin that is still damp, whichever suits you. You can get dressed straight away.

The scent is fresh, soft and floral, and it stays on the skin long enough for other people to notice. That is what orange blossom smells like.

At our shop in Sarajevo City Center you can give it the same test before you take it home.

Nobody needs a definition to tell milk from butter in the fridge. Skin is the same: the difference shows straight away, on the inside of your forearm.