Along with antibiotics, benzoyl peroxide (BP) is one of the most studied topical acne treatments. Without going into details, studies show BP is as effective as topical antibiotics, with the advantage that bacteria cannot develop resistance to BP.
2.5% is the optimal concentration as there’s no evidence that higher concentrations are more effective. And, higher concentrations cause significantly more skin irritation. About 2.5% of the patients have ‘allergy’ to BP, and for these people, exposure to BP causes severe skin irritation, redness, and dryness. Others are likely to experience mild skin irritation and dryness.
Despite popularity, the effectiveness of salicylic acid as an acne treatment has never been adequately studied. I could only find a few older studies that showed SA to be more effective than a placebo lotion. However, there are no good studies comparing SA to benzoyl peroxide or retinoids. In most studies, SA is used as a secondary therapy and combined with antibiotics or retinoids. But such studies aren’t very helpful for our purposes.
Fortunately, in 2013, Zheng et al. tested a cream with 1.5% SA and a blend of antioxidants. The cream reduced the number of inflammatory pimples by 61% and non-inflammatory pimples by 74%. I have to ask you take these results with a grain of salt as this was not a very rigorous study.
Most dermatologists considered SA as less effective than BP or tretinoids and usually used either as an adjuvant therapy or for people who cannot tolerate the more effective treatments. Higher concentrations carry a risk of causing hyperpigmentation.
Unlike most other ingredients, salicylic acid can penetrate the skin and make it to the systemic circulation. When applied on a large area of the skin, it can cause salicylism or aspirin poisoning. Review of literature shows that you would have to apply 6% SA lotion on 40% of your body area for this to become a problem. For most people with acne never get even close to such exposure levels. This can be an issue for someone using prescription creams for psoriasis or other skin conditions that cover a larger area.
The bottom line is that SA has a place in a well-rounded acne treatment regimen. Its keratolytic properties help to keep the skin pores open, and it’s non-irritating and safe for most people. However, it should be combined with topical antioxidants and antibacterials to improve effectiveness.
Study in the International Journal of Cosmetic Science compared the effectiveness of 5% vitamin C (as sodium ascorbyl phosphate, SAP), 0.2% retinol or their combination. After 8 weeks acne was reduced by 48% in the vitamin C group, by 50% in the retinol group, and by 63% in the combination group. No adverse reactions were noticed in any group.
Ascorbyl acid (AA), the form of vitamin C you’ll find in supplements and foods, is unstable and difficult to formulate with. That’s why many companies formulate with more stable vitamin C derivatives, like sodium ascorbyl phosphate (SAP) in these acne studies. We don’t have any data to show which of the derivatives is the best. That’s why I would suggest going with products that contain either sodium ascorbyl phosphate or magnesium ascorbyl phosphate, both of which are similar in function and SAP has been proven to work against acne.
Another study compared 5% SAP lotion to 5% benzoyl peroxide. 77% of the people treated with the SAP lotion showed good to excellent results as compared to 61% in the BP group. Similarly, nobody in the SAP group showed worsening of acne vs. 2 people in the BP group.
Another study compared 5% SAP lotion to 1% clindamycin gel. 79% of the SAP group showed good to excellent results as compared to 39% in the clindamycin group.
Yet another study showed that 61% of the participants improved after 5% SAP lotion as compared to 38% improved in the placebo group.
A study in the International Journal of Dermatology showed that 4% vitamin B3 gel worked better than 1% clindamycin gel. In the vitamin B3 group, 82% of the participants improved and acne severity reduced on average by 52%, as compared to in the clindamycin group where 68% improved and acne severity went down by 38% on average.
Effat Khodaeiani et al. also tested 4% vitamin B3 gel against 1% clindamycin gel in 80 people with moderate acne. The results showed 72% reduction in acne in both groups. Sub-group analysis showed that the vitamin B3 gel worked better for participants with oily skin than for those with dry skin.
Morganti et al. tested 4% vitamin B3 and linoleic acid emulsion against 1% clindamycin in 90 patients with inflammatory acne. The vitamin B3 emulsion was more effective by all measures. After 12 weeks there was a 48% reduction in acne in the vitamin B3 group as compared to 35% reduction in the clindamycin group. The B3 emulsion also protected the skin against chlorine-induced skin irritation (such as what happens when you swim in a pool) whereas the antibiotic showed only minor protective effect.
So far four studies have tested green tea preparations against acne, with most studies showing around 50% reduction in acne.
Yoon et al. showed EGCG targets all the pathogenic mechanisms behind acne. They showed EGCG can reduce sebum production in skin cells, suppress P. Acnes induced inflammation, and inhibit bacterial growth. They tested 1% and 5% EGCG cream against placebo in 35 patients with moderate acne. After eight weeks, EGCG treatment reduced non-inflammatory lesions (whiteheads, blackheads, and comedones) by 79% and inflammatory acne by 89%. There was no difference in effectiveness between the 1% and 5% EGCG creams.
Elsaie et al. tested 2% EGCG lotion in 20 Egyptian patients with moderate acne. Average pimple count dropped by 58% (from 24 to 10) in 6 weeks, and 85% of the participants saw 50% or better reduction in acne. 15% of the patients complained about mild itching of the skin.
In 2006, Sharquie et al. tested 2% green tea lotion against placebo in 60 patients with mild to moderate acne. The average reduction in pimple count for the green tea lotion group was 49% (33 to 17) in comparison with 9% (32 to 29) in the placebo group.
In 2008, Sharquie et al. tested 2% green tea lotion against 5% zinc sulphate lotion in the treatment of mild to moderate acne. The green tea lotion reduced acne on average by 47% (50 to 26.5) as compared to 23% (39 to 30) reduction in the zinc sulphate group.
While these results seem promising, most of the studies are small and not very rigorous. Such studies tend to produce false positive results or exaggerate the effects. In other words, take these with a grain of salt.
Tea tree oil
Several studies have shown tea tree oil to be effective against acne. Studies have shown it to be as effective as benzoyl peroxide or topical antibiotics. I’ll go over the most interesting ones here.
Basset et al. compared 5% TTO lotion to 5% benzoyl peroxide lotion. They found that while BP worked faster, there was no difference in effectiveness at the end of the study. The TTO group experienced fewer side-effects.
Darabi et al. showed that 5% TTO is more effective than topical erythromycin (an antibiotic).
Malhi et al. tested commercially available TTO products and demonstrated that combination of tea tree facial wash and acne treatment gel reduced acne by 54% in 12 weeks. Here are the products used in the study:
Fabbrocini et al. showed resveratrol creams may have potential as acne treatments. The researchers asked 20 young adults to apply resveratrol cream on one side of the face and a placebo cream on the other side.
After two months, there was a 54% reduction in acne at the resveratrol-treated side and a 6% reduction in the placebo-treated side. Furthermore, the skin area containing ‘microcomedones’ (blocked pores, the earliest state of a pimple) went down by 67% and 10% in the resveratrol and placebo-treated sides respectively. This shows that resveratrol can interfere with the earliest stages of the acne formation process.
Licorice, l-carnatine and 1,2-decandediol
A study published in Journal of the European Academy of Dermatology and Venereology showed that a multi-ingredient cream reduced inflammatory acne by 70% (vs. 20% reduction with a placebo) and sebum production by 19% (vs. no change with the placebo) in 60 14 to 40-year-old participants. The cream contained licochalone (licorice extract, antioxidant), l-carnatine and 1,2-decanediol (antibacterial).
Vitamin B3, retinol and vitamin D
Another study tested the combination of 4% vitamin B3, 1% retinol, and 0.5% 7-dehydrocholesterol (provitamin D, converted to vitamin D3 in the skin) moisturizer on back acne. After 45 days, 94% of the patients showed improvements in acne with 6% being completely clear, 25% showing very good results and 63% showing moderate/good results.