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In any topical preparation, the active ingredient is mixed with a chosen vehicle to allow its delivery into the stratum corneum and to maintain the stability of the drug. Increased penetration of a drug can occur if the skin is inflamed or applied in occluded sites.

The majority of topical preparations used for vulval disorders are either ointments or creams. Gels and lotions often sting and are not widely used, but may be helpful in the hair‐bearing mons pubis area. Ointments are water‐in‐oil emulsions and form an impermeable layer over the skin that prevents evaporation of water (Figure 8.1a). Due to their occlusive and hydrating effects, they can increase penetration of the drug. They are stable compounds which rarely require the addition of preservatives and hence have a much lower risk of inducing a contact allergy.

Figure 8.1 (a) Ointments are thicker and greasy to apply, but better to use in the anogenital area. (b) Creams are thinner and apply easily, but contain more excipients.

Creams contain oil and water. They are less greasy than ointments and spread more easily (Figure 8.1b), but their high water content requires the addition of preservatives to prevent contamination by bacteria and fungi, and to prolong shelf life. It is important to remember that preservatives, stabilisers, and other additives are all components of topical treatment, and if the cutaneous problem flares after application of the preparation, it may be due to an allergic contact dermatitis to one of these agents and should be investigated as such (see Chapter 22).