Here is a list of botanicals, vitamins, minerals and supplements that have been studied for acne.
Topical Vitamin C
5% sodium ascorbyl phosphate (stable, water-soluble form of vitamin C that is commercially available) has been shown to work better than 5% benzoyl peroxide. Topical vitamin C is also a great treatment for dark spots following acne lesions.
Tea Tree Oil
Topical tea tree oil seems to work well as benzoyl peroxide and is less irritating. Could cause contact dermatitis (localized skin reaction) with burning, dryness and itching.
Topical Green Tea
Green tea 2% lotion & 1% solution have been studied for acne with possible application site stinging and irritation.
Oral zinc gluconate (not sulfate) as well as topical 4% erythromycin - 1.2% zinc acetate gel/liquid works for acne but oral zinc may cause nausea, vomiting or stomach pain.
Nicotinamide (amide form of vitamin B3, also known as niacinamide)
Both topical and oral (Nicomide, Nicazel) forms have been studied for acne. In one study 4% nicotinamide emulsion worked better than topical antibiotics (1% clindamycin emulsion)
Study involved combination of tretinoin cream and aloe vera emulsion with possible scaling and redness
Natural phenol found in the skin of grapes, blueberries and raspberries. Resveratrol gel daily was studied for acne with no known side effects.
Omega Fatty Acids
Omega 3 fatty acid and omega 6 may be effective and safe treatments for acne.
Study published in Journal of Drugs in Dermatology: