Topical dermatological products are designed as delivery systems to apply medication or moisture directly to the skin. The base formulation influences how active ingredients penetrate the skin barrier and how they feel upon application. Creams and ointments are the two most common vehicles used for therapeutic and cosmetic purposes. Choosing the correct base is important for maximizing the intended effect, as the physical properties of the vehicle dictate its functional role on the skin.
Defining the Core Difference: Oil and Water Ratios
The fundamental distinction between creams and ointments lies in the proportion of oil and water they contain, which determines their classification as different types of emulsions. Ointments are predominantly composed of oil, typically containing around 80% oil and 20% water or less. This high lipid content often results in a base that is anhydrous or nearly so; petrolatum or mineral oil are common primary ingredients.
Because of this oil-heavy composition, ointments do not readily mix with skin secretions. They remain primarily on the skin’s surface, forming a lasting protective layer. This formulation ensures that the medicinal agent is concentrated at the application site and is not easily washed away.
Creams, in contrast, are semisolid emulsions where the oil and water phases are more equally balanced, often approaching a 50% oil to 50% water ratio. They are typically formulated as oil-in-water emulsions, meaning the water is the continuous phase and the oil is dispersed within it. This balance allows them to spread more easily and be readily miscible with water, making them washable from the skin and clothing.
Some creams are formulated as water-in-oil emulsions, which can be slightly greasier and offer more emollient properties than the oil-in-water types. This compositional difference dictates the physical interaction of each product with the skin.
Physical Properties and Skin Feel
The different oil-to-water ratios translate into distinct physical attributes and sensory experiences on the skin. Ointments have a thick, viscous consistency that is noticeably greasy and shiny upon application. This heavy texture is a result of the high oil concentration, which makes them highly occlusive, meaning they form a substantial physical barrier on the skin.
This enhances hydration and drug penetration, but also means ointments are not absorbed quickly and can feel heavy or sticky. Their barrier function provides a protective shield against external irritants by significantly limiting transepidermal water loss (TEWL).
Creams have a lighter, softer texture that is generally less greasy, making them more cosmetically acceptable for daily use. Their higher water content allows for easier spreading over larger surface areas compared to the stiffer nature of an ointment. As the water phase of a cream evaporates after application, it can produce a temporary cooling sensation on the skin.
Creams are considered semi-occlusive or non-occlusive, meaning they do not form the same impermeable barrier as ointments. They are absorbed more quickly into the skin layers due to their continuous water phase. This faster absorption makes them feel cleaner, but they provide less intensive barrier protection or prolonged moisturizing effect than their oilier counterparts.
Indications for Use
The practical choice between a cream and an ointment depends largely on the skin condition being treated, the location of the application, and the desired therapeutic effect. Ointments are recommended for chronic, dry, or thickened skin conditions, such as eczema, psoriasis, or cracked heels. Their superior occlusiveness maximizes the moisturizing effect and enhances the potency of any incorporated medication by increasing its penetration into the skin.
Because of their greasiness, ointments are best avoided in intertriginous areas, which are skin folds like the groin or armpits, where they can trap heat and moisture. They are also less suitable for hairy areas where they may be difficult to apply or cause folliculitis. The intense moisture they provide is often best utilized for nighttime application.
Creams are the preferred vehicle for acute, weeping, or inflamed skin lesions, as their drying effect from water evaporation can be soothing. They are the ideal choice for application over large body surface areas and in regions where a greasy residue is undesirable, such as the face or hands during the day. Creams are better tolerated in skin folds and on hairy skin due to their lighter, more spreadable consistency.
When the same active ingredient is available in both forms, the ointment is chosen for maximal drug effect and hydration of very dry skin, while the cream is selected for its cosmetic acceptability and suitability for moist, inflamed, or sensitive areas. The goal is to match the vehicle’s properties with the physiological state of the skin lesion to achieve optimal efficacy.