Fig 2.10 Lotions, Creams and Ointments
n C/5
2
2
G 55 C/5
n
LOTIONS Most liquid Water suspensions or Oil-in-water emulsions
CREAMS Less liquid Oil-in-water or Water-in-oil emulsions
OINTMENTS Least liquid All oil or fat (no water)
Fig 2.11 Oils and Fats in Emollients
Types of emollient Lotions, creams and ointments (Fig 2.10) Formularies such as the British National Formulary provide basic introductory information on the chemical properties and constituents of the vast array of emollients available. Ointments are thicker and less easy to use than creams, and creams are thicker than lotions. Lotions can be suspensions, or emulsions. Suspensions, or shake lotions, contain insoluble powders and have little use in treating atopic skin disease. Lotions that are oil-in-water mixtures need an emulsifying agent to maintain the mixture. Additional active substances can be dissolved in either phase. Oil-in-water lotions are also rarely useful in atopic skin disease as their moisturising effect is short-lived and their lubricating function is minimal. They are however cooling in their effect, and may be useful in treating hairy skin. Creams may be either oil-in-water or water-in-oil emulsions. The type is determined by the emulsifying agent used. Once applied most of the water evaporates, though some is absorbed by the superficial epidermis. The most relevant effect is the film of oil left on the skin surface. The oils used in creams may be synthetic, or may be mineral, animal or vegetable in origin. As with lotions, added ingredients can be dissolved in either phase of a particular cream. Ointments are the most greasy of these three preparations. As they are more occlusive than creams, they are particularly suitable for chronic, dry lesions. Ointments do not contain water, but added constituents such as macrogol can make them easier to rinse off the skin. Various types of paraffin or petroleum jelly provide the bases of most popular ointments, but oils and fats from animal and vegetable sources are also used, as are those of synthetic origin (Fig 2.11).
Mineral, e.g. petroleum jelly
Animal, e.g. lanolin
Vegetable, e.g. arachis oil
Synthetic, e.g. cetomacrogol
18
Additives Additional substances in lotions, creams and ointments are introduced with a variety of intentions. These include improving their user-friendliness, adding preservative and anti-inflammatory functions, and providing additional penetrating and hydrating qualities to the topical treatment. These various effects need to be balanced against possible side-effects, in particular hypersensitivity.