logo Topical therapy for acne and rosacea

Follicular skin diseases

Topical therapy for acne and rosacea

Objectives

  • Prescribe topical therapy for acne and rosacea safely and appropriately.

Key points

  • Topical therapy should be applied to all the areas affected by the skin condition.
  • Adverse effects of topical acne medications include dryness, irritant and allergic contact dermatitis.
  • Topical retinoids are most often used to treat acne and photoageing. They should not be prescribed in pregnancy.
  • Benzoyl peroxide is antiseptic, keratolytic, comedolytic and anti-inflammatory.
  • Azelaic acid is derived from Malassezia yeasts. It is antibacterial, keratolytic, comedolytic, anti-inflammatory and reduces pigmentation.
  • Topical clindamycin and erythromycin reduce the number of Propionibacterium acnes and are anti-inflammatory. They should be used with another acne agent to reduce the likelihood of bacterial resistance.
  • Metronidazole reduces inflammatory lesions in rosacea.

Introduction

Topical therapy is used alone in mild facial skin conditions, and combined with oral antibiotics if more severe. As it may take weeks to months to notice improvement, it should be applied to all the areas that are affected by the skin condition and continued until the condition has resolved.

Topical therapy for acne includes:

Topical therapy for rosacea includes:

Side effects of topical agents

Dryness caused by topical retinoid

Irritant dermatitis due to benzoyl peroxide


Topical retinoids

Retinoids (vitamin A derivatives) are defined by their ability to bind nuclear retinoid receptors. They control cellular proliferation and differentiation. Available topical retinoids include:

Tretinoin, isotretinoin and adapalene are prescription medicines for the treatment of acne with particularly useful effect on comedones. Continued use generally also reduces inflammatory lesions in acne and rosacea but initially they may appear to aggravate these.

Topical retinoids (prescribed and over-the-counter) are also useful to reverse photoageing. They peel off and lighten pigmented lesions (lentigines) and reduce fine surface wrinkles by preventing loss of collagen from, and stimulating new collagen formation in, the papillary dermis. They have a similar but less obvious effect on aged skin in non sun-exposed sites.

Topical retinoids can be applied to any area but are most often used on the face, the neck and the back of hands. They frequently irritate and may increase the risk of sunburn. Excessive use results in redness and peeling. These effects can be minimised by using a minimal amount on alternate nights at first and if necessary applying a light oil-free moisturiser.

There is continuing controversy whether the topical use of tretinoin, isotretinoin and adapalene could cause birth deformities so they should not be prescribed in pregnancy.

Benzoyl peroxide

Benzoyl peroxide is a commonly used topical treatment for mild to moderate acne. It is safe for adults and children, and can be used in pregnancy.

Benzoyl peroxide has the following properties:

Benzoyl peroxide is available as cream, gel, lotion and wash at concentrations of 2.5%, 5% and 10%. It may be combined with other topical or oral therapy.

In New Zealand, products containing benzoyl peroxide are available without prescription. Some of these are listed in the New Ethicals catalogue.

How to use benzoyl peroxide products:

Azelaic acid

Azelaic acid is a natural material produced by Malassezia yeasts, and is a normal dietary constituent. It is available over-the-counter as a 20% cream and lotion to treat mild comedonal and inflammatory acne, and rosacea.

It is antibacterial, keratolytic, comedolytic and anti-inflammatory

Azelaic acid also reduces pigmentation, so it's particularly useful for darker skinned patients whose acne spots leave persistent brown marks or who have melasma.

The cream should be applied to the area affected by acne initially daily, then if tolerated building up to a generous twice-daily application after thoroughly cleansing the skin.

Azelaic acid is nontoxic and is well tolerated by most subjects. However, atopics and others with sensitive skin may find it irritating.

Topical antibiotics

Antibiotics reduce the number of Propionibacterium acnes on the skin surface and in the follicles and also have an anti-inflammatory action.

Topical antibiotics marked for acne contain clindamycin or erythromycin as a lotion, solution or gel. They should be applied once or twice daily, preferably while also using another acne agent such as benzoyl peroxide or topical retinoid. However, combined use may result in a cumulative irritant effect.

Metronidazole is an antiprotozoal and anaerobic antibacterial agent. The mechanisms by which topical metronidazole acts in reducing inflammatory lesions of rosacea are unknown.

These topical antibiotics are not on the Pharmaceutical Schedule in New Zealand so they are not subsidised.

Other topical agents

Salicylic acid, sulphur, sulphacetamide, resorcinol and alpha-hydroxy acids are present in many over-the-counter preparations for acne and rosacea. Various combinations have comedolytic, keratolytic and anti-inflammatory effects but there is little published evidence to support their use.

Brimonidine gel is a fast-acting vasoconstrictor and may be used to reduce facial erythema. The main disadvantage is variable post-treatment rebound, which is rarely severe but can be uncomfortable.