DERMATOLOGY (Formulary)

Refer to the extensive clinical guidelines at the end of the chapter. For NHS Highland guidance on the treatment of head lice and scabies refer to guidance. 

The National Dermatology Patient Pathways (available at www.dermatology.nhs.scot/dermatology-pathways/pathways and via the NHS Highland Intranet under Shared Clinical Guidelines) should be used in association with drug recommendations and guidance in this chapter to inform the management of acne, alopecia, atopic eczema, benign skin lesions, generalised and local pruritus, hand and foot eczema, molluscum contagiosum, nail dystrophy, non-melanoma skin cancers, psoriasis, rosacea, scabies, solar (actinic) keratoses and Bowen’s Disease, suspicious pigmented lesions, urticaria, and viral warts.  Also refer to the British Association of Dermatologists Clinical Guidelines at British Association of Dermatologists (bad.org.uk).

For use of dermatologicals in children, refer to BNF for Children.

Vehicles

Choice of vehicle is very personal; it can mean the difference between treatment success and failure. Skin treatments are ‘worn’, like clothes.  Patients will not use a topical therapy that irritates their skin, and will be reluctant to use one that does not ‘feel right’.

Ointments are recommended as the first choice of formulation for most skin diseases and are particularly useful for dry, scaly conditions.  Ointments are greasy and generally insoluble in water so can be difficult to wash off; they do not suit all patients and may be less acceptable to some patients.

Creams, emulsions of oil and water, often contain an antimicrobial preservative and are therefore more likely to cause both irritant and allergic reactions. For this reason creams are often best avoided as first-line treatment, but can be better than ointments for some acute conditions due to a cooling effect as they evaporate.  Creams may be more cosmetically acceptable for some patients in some body sites and are often the agents of choice for moist, flexural areas such as axillae.  

Lotions also have a cooling effect, and may be preferable to treat hairy sites.  They can be made up in either water or alcohol. Alcoholic lotions will sting if applied to broken or acutely inflamed skin.

Gels have a high water content, and are especially suitable for the face and scalp; however, gels may irritate in some circumstances.

Adverse reactions to topical therapy.

• Topical medications include any balm, cream, gel, oil, lotion, patch, ointment, or any other product with a medicinal ingredient that is applied to the skin.
• An allergy to a topical medication can produce a range of reactions such as irritant contact dermatitis, allergic contact dermatitis, contact urticaria, photosensitivity or anaphylaxis (rarely occurs but can be fatal).
• Adverse reactions due either to irritation or contact allergy can be difficult to differentiate clinically, although immediate stinging is likely to be irritant in nature.
• Irritant reactions can affect anyone, but are more likely in atopic patients who tend to have dry, sensitive skin. They are more common with creams, which contain preservatives, biocides and emulsifiers than with ointments. Irritant facial conditions, such as rosacea, are more commonly irritated by gel preparations, which often contain propylene glycol, than by creams.
• Allergic reactions are less common and usually involve the immune system via a Type IV delayed hypersensitivity reaction, which can be investigated by patch testing. They should be suspected if the skin condition worsens or extends to other areas while on treatment and usually take 3 to 4 days to develop.
• Contact urticaria results in a local burning sensation, tingling, itching may occur within minutes to about 1 hour after contact with the skin. Rash usually resolves by itself within 24 hours of onset.
• A photosensitivity rash is caused by the interaction of sunlight with an ingredient in the product.
• Any topical agent can cause an allergic reaction, although some are more likely to than others, particularly topical antihistamines, local anaesthetics, antibiotics and creams, rather than ointments. The reaction may be due to an active ingredient, eg hydrocortisone or neomycin, or to an excipient, eg a preservative or emulsifier: related agents may cross-react. All ingredients are listed in the Summary of Product Characteristics (emc.medicines.org.uk/).