Topical Treatments for Acne

By

Michael H. Berkson, M.D.

Acne that is mild or moderate in severity can often be adequately treated by the use of topically (externally) applied agents.  Some acne topicals are available over the counter while others require a prescription.  They come in a wide variety of formulations known as vehicles.

The most common topical vehicles are creams, lotions, gels and washes.  Acne topicals can be used alone, or in more moderate to severe cases, combined with systemic medications such as oral antibiotics.

One of the advantages of topical treatments is that most have minimal absorption and thus have less potential for systemic side effects such as allergic reactions, gastrointestinal upset, yeast infections, headache, and generalized sensitivity to sunlight. Side effects of topicals generally take the form of irritant reactions and sometimes increased sensitivity to the sun localized to the area of application. The use of topicals is mainly limited by the fact that sometimes they are not strong enough to control the breakouts when used alone.  In these cases combining topicals with oral medications might be indicated.

There are three main categories of topical medications that are used to treat acne:  Retinoids; Benzoyl Peroxide; and Antibiotics. Then there are combination products and miscellaneous topicals that don’t fit into the three major groups.

Retinoids

Retinoids are molecules derived from vitamin A that attach to retinoid receptors in the cell and affect cellular processes such as gene transcription and protein synthesis.  Retinoids are relevant in the treatment of acne because they inhibit the formation of comedones (comedogenesis) and  also have anti-inflammatory properties. Retinoids can also speed the resolution of the dark spots- post inflammatory hyperpigmentaion- that sometimes persist after breakouts of inflammatory acne.

There are three different classes of retinoids.  They include tretinoin ( Retin A), adapalene ( Differin), and tazaretene (Tazorac). All come in several different strengths and are available in cream and gel vehicles.  Differin gel is now available without a prescription in the 0.1% strength.

The topical retinoids are effective as single agents in mild acne, and are also useful in more moderate and severe acne, especially when combined with other topicals and/or systemic treatments. The most common side effect of topical retinoids is retinoid dermatitis, which usually occurs during the initial weeks of treatment. This usually takes the form of redness and peeling of the skin that may be accompanied by stinging and burning. The retinoid dermatitis tends to abate on its own but can be minimized by starting with lower strength preparations, applying the product sparingly, and avoiding face washing immediately prior to application.  Retinoids can also increase one’s sensitivity to the sun and may make the skin more fragile and vulnerable to minor trauma from waxing and threading procedures.

Benzoyl Peroxide

Benzoyl peroxide (BPO) is an antimicrobial agent that works via a different mechanism than antibiotics and is highly effective at killing the P. acnes bacteria in the sebaceous follicle, thus reducing inflammation.  BPO is also moderately effective at clearing and preventing the formation of new comedones.  It can be used as a stand-alone treatment for mild acne or combined with topical or oral antibiotics and/ or retinoids in more severe cases.  When used concurrently with topical or systemic antibiotics, benzoyl peroxide can help reduce the chance of the development of bacteria that are resistant to the antibiotic.

BPO is available in many different vehicles including washes, lotions, creams, and gels. It comes in strengths ranging from 2.5 to 10%.  Most BPO preparations (Panoxyl, OXY, and Persagel) are sold over the counter (OTC), but there are still a few variations that are prescription only (Triaz). The difference between OTC and prescription BPO is probably inconsequential.  The main side effect of BPO is that it bleaches colored fabrics such as towels, clothing, and linens. Some people notice dryness and irritant skin reactions, especially at the start of treatment. Allergic skin reactions( contact dermatitis) occur infrequently.

Topical Antibiotics

Topical antibiotics still play a role in the treatment of mild to moderate acne, especially in combination with benzoyl peroxide.  Clindamycin and erythromycin are the two antibiotics that are currently available for the topical treatment of acne. A topical version of the potent oral antibiotic, minocycline, will also be available in the near future.  Erythromycin is now rarely used  because of the high degree of bacterial resistance that has developed to the drug over the years.. Both clindamycin and erythromycin disrupt bacterial protein synthesis and thus decrease the populations of P. acnes in the sebaceous follicle which in turn reduces inflammation. The use of topical (and oral) antibiotics should always be accompanied by the use of BPO which helps to decrease the chance of developing bacterial resistance to the antibiotic.

Combination Topicals

There are a number of topicals that contain two different drugs in one product.  One advantage is convenience, in that instead of applying two different medications separately, with combination products there is only the need for a single application.  There is also the advantage of synergy, meaning that the combined effect of the two components is greater than either by themselves, primarily because each works by a different mechanism.  Also, in the case of antibiotic+BPO products, the BPO helps reduce the chance of developing bacterial strains that are resistant to the antibiotic. Finally, an antibiotic in combination with a retinoid may help reduce the incidence and severity of retinoid dermatitis via the anti-inflammatory effect of the antibiotic.  Some currently available combinations include clindamycin+ BPO( Duac and Benzaclin), erythromycin+BPO (Actipak), clindamycin+tretinoin (Ziana and Veltin) and adapalene+BPO ( Epiduo and Epiduo Forte).

Miscellaneous Topicals

There are a variety of topical medications and products that are used to treat acne that do not fit into the three primary categories.

Salicylic acid is a beta hydroxy acid that is derived from from a compound found in the bark of the willow tree.  It is found in many over the counter acne washes and, in higher concentrations, can also be used as a chemical peel. It can be helpful in mild acne and is particularly helpful at reducing comedones.

Glycolic acid is an alpha hydroxy acid  that is derived from sugar cane. It is active against comedones and also has a mild anti-inflammatory effect.  It is available in  many different forms including washes, creams, sprays, and chemical peels. Glycolic acid containing acne products are available over the counter and are also commonly sold in dermatologists’ and cosmetic surgeons’ offices and medispas.

Azelaic acid is found in wheat, rye and barley.  It is available by prescription in the form of a cream or gel ( Azelex and Finacea) and can be useful  as a single treatment for milder acne, and as part of a combination for more moderate breakouts.  It is active against comedones and is mildly anti-inflammatory. Another advantage of azelaic acid is that, like retinoids, it inhibits pigment production by melanocytes and can help resolve the hyperpigmentation that often results after the inflammatory pimple resolves.

Topical dapsone (Aczone) is a sulfone type of antimicrobial that can be helpful in mild to moderate inflammatory acne.  It’s action in acne is primarily anti-inflammatory. It is convenient in that it only needs to be applied once daily and tends to be less irritating than either the retinoids or BPO.

Sulfur and sodium sulfacetamide are available over the counter, and by prescription, in the form of washes creams lotions and foams.   They are best used for mild to moderate inflammatory acne. Their advantages are that they tend to be less irritating than retinoids and BPO and sometimes have a tint incorporated in the formulation that can partially neutralize the redness of the acne.

The next article will be on the subject of systemic ( oral) medications for the treatment of acne.

References:

An Overview of Acne Therapy, Part 1: Topical therapy, Oral Antibiotics, Laser and Light Therapy, and Dietary Interventions.  Marson JW, Baldwin HE.  Dermatol Clin. 2019 Apr;37(2):183-193.