Leave-on topical emollients

As the name suggests ‘leave on topical emollients’ are ones that are applied to the skin and left in place, not washed off.

Lotions
Lotions have a high level of water in them and are therefore easy to use. They are readily absorbed into the skin and do not leave it feeling greasy. Because of these features most cosmetic emollients fall into this category. They are not, however, very effective for those with a dry skin condition. Some products in certain conditions (hot, dry weather) may actually dry the skin as the high level of water in the product evaporates off the skin taking natural moisture with it and thus making the skin even drier.

Creams
Creams are a mixture of water in lipid, generally there is more lipid than water. These products absorb into the skin relatively quickly, but are thicker and greasier than lotions. The water and lipid combination of both creams and lotions creates a number of challenges with regards to maintaining a stable product. Emulsifiers have to be added to ensure that the lipid and water emulsion stay together and preservatives are needed to prevent bacterial contamination.

Ointments
Ointments fall at the very greasy end of the emollient continuum. They do not contain any water and therefore there is no need to add preservatives. This does not necessarily mean that there are no potential sensitisers in ointments as there may be other ingredients added to stabilise or enhance the effectiveness of the product. Preservatives are not needed in lipidonly products (i.e. ointments) as there is no medium for bacterial growth. Therefore, whilst these are the heaviest, greasiest emollient products, they are the ones that are least likely to cause sensitisation. The consistency of ointments is affected by ambient temperature. Warmth will soften ointments, which may appear quite hard and unpliable whilst in the pot.

Sprays
Emollient sprays contain lipids such as white soft paraffin, liquid paraffin and fractionated coconut oil. Propellants, for example butane and isobutene, are added to ensure that the emollient is ejected from the can in a spray format over the skin. Some spray emollients use a ‘bag in a can’ technology. This means that the spray can be effectively sprayed at any angle and that the emollient is kept totally separate from the propellant.

Gel emollients
These are oil and water products; however, the way that they are emulsified is different from normal creams and lotions. The carbomer gelling agent holds the oil and water together whilst it is in the bottle (and gives the product its typical ‘jelly-like wobble’); however, when it is applied to the skin, the gelling agent dissolves and allows the oil and water to separate. This has the impact of allowing the oil to stay on the skin longer and not to be vulnerable to being washed away.

Method of application
There does not seem to be a scientific word for the science of topical emollient application. This is reflected in the fact that the literature is virtually devoid of any experimental data about how topical emollients should be applied to the skin to achieve maximum therapeutic effect. Indeed there are significant questions over such basic questions as ‘Do medicinal bath oils offer any benefit?’ ‘Which should be applied first to the skin, a topical emollient or a topical steroid?’ Thus much of the practice in relation to emollient use is based upon ‘custom and practice’ and deriving appropriate techniques from first principles.

When considering methods of emollient application, there are five questions for which it would be useful to have answers, in order to guide practice. These are:

• How much topical emollient to apply?
• How frequently to apply the topical emollient?
• When to apply the topical emollient – which includes when to apply it in relation to other topical medicines?
• How to physically apply the topical emollient?
• Where to apply the topical emollient?

Literature reviews reveal that there is precious little scientific evidence to guide practice in any of these areas (Penzer, 2005; Ersser et al., 2007), which means that guidance offered in textbooks and journals is based on clinical practice and experience.

The other factor that should be taken into account when prescribing emollients is that patients with dry skin conditions have to ‘wear’ their treatments. How it feels on their skin, how easy it is to apply and whether there is a smell associated with it, all impact on whether someone will use the emollient or not. No single emollient will suit everyone, and there is no doubt that patients need to experiment with different types of emollients before they settle on one or two that suit them (All Party


Parliamentary Group on Skin, 2006). Because the skin can feel different depending on climate, it is possible that individuals may need alternative emollients at different times of the year. For example, in winter, a heavy greasy emollient may feel fine, but in the summer months something lighter might be preferable.