Common Topical Treatments for Acne
Topical treatment are usually the first choice for those with mild to moderate acne. Most topical treatments are applied as a thin layer all over the entire face, not just to individual spots. Some topical treatments have the potential to be irritating to the skin and it is advisable to use the treatment initially on a small area of affected skin. Commonly used anti-acne agents include:
Benzoyl peroxide (BPO) is a powerful antimicrobial agent with anti-inflammatory, and comedolytic properties. It is commonly available in a number of different formulations and concentrations (2.5%, 5% , or 10%) and can combined with a variety of other topical agents. It is most efficacious against superficial inflammatory lesions, but also has some effects on non-inflammatory acne by reducing hyperkeratosis.
BPO’s lipophilic properties allow penetration into the pilosebaceous unit to act on both surface and ductal bacteria and yeast. Once applied to the skin, BPO decomposes to release free radicles which are bactericidal and anti-inflammatory. BPO is useful as it is not associated with bacterial resistance, which can be a problem with topical antibiotics.
When first applied, BPO can sometimes cause mild redness/ burning/ and peeling. It can also bleach hair and clothing and has a potential to cause allergic contact dermatitis in 1-2.5% of patients. These effects can be eased by reducing the frequency of application. Patients usually become tolerant of these effects as treatment continues.
Topical antibiotics work by reducing the numbers of C. acnes bacterium in the sebaceous follicles, reducing the inflammation from acne. The most commonly used antibiotics include erythromycin, clindamycin, and tetracycline. Due to the emergence of bacterial resistance, use of topical antibiotic monotherapy is not recommended. Treatment efficacy is increased when combined with benzoyl peroxide e.g clindoxyl gel. Treatment with topical antibiotics should only be continued until any visible clinical improvement ceases.
Topical Retinoids are vitamin A derivatives. They are available in the form of: Tretinoin (0.01%,0.025%, 0.05%, and 0,1%), its isomer Isotretinoin (0.05%), and a 3rd generation retinoid like drug Adapalene (0.1%). Topical retinoids are beneficial for both comedonal and inflammatory acne.
Retinoids work by inhibiting development of the microcomedo and mature comedones. They do this by promoting normal follicular epithelium desquamation, decreasing cohesiveness of keratinocytes, and reducing follicular occlusion to help to “unplug” pores. Retinoids also decrease P. acnes growth, and provides a microenvironment less favourable for the development of inflammation.
In addition to treatment of active acne, retinoids also accelerate the resolution of acne- induced post-inflammatory hyperpigmentation and are often used as long-term maintenance therapy.
When starting retinoids, some patients may experience an initial flare of their acne. This can be minimized by starting retinoids at lower concentrations and incrementally increasing preparation strength. Skin irritation ( redness, dryness peeling) is also another common side effect but tolerance usually occurs after 1-2 months of continuous application. To minimise irritation, harsh soaps, toners, astringents, alpha hydroxy acid of salicylic acid products should be avoided. Decreasing frequency of application of application to every other or every third night can also be considered if irritation is a problem. Retinoids have the potential to cause photosensitivity, hence they are best applied at night and excessive UV exposure should be avoided.
Topical tretinoin should not be applied at the same time as BPO. BPO makes tretinoin less stable due to its oxidative effect, worst during light exposure. Adapalene and BPO however, may be used together.
The use of topical retinoids is not recommended in pregnancy. Oral retinoid are teratogens. Significant absorption of topical retinoids has not been demonstrated. However, female patients using topical retinoids should avoid pregnancy and discontinue use immediately if pregnant.
Azelaic acid is a naturally occurring dicarboxylic acid with mild comedolytic with anti-inflammatory properties. It is usually available in a 15% gel or 20% cream. It can be used for treatment for both inflammatory and comedonal acne. Azelaic acid has an inhibitory effect on tyrosinase and can improve post-inflammatory hyperpigmentation