Evidence-Based Reviews
Active ingredients, explained by the research.
We read the studies so you know exactly what each ingredient does, at what concentration, and why. No marketing claims without citations.
No brand pays for editorial placement. Telehealth affiliate links disclosed on each page.
Active Ingredients at a Glance
Every major skincare active with a documented mechanism and clinical data behind it.
Tretinoin
PrescriptionThe gold standard retinoid. Rx only in the US. 201K monthly searches.
Retinol
OTCOTC retinoid with a gentler onset. Entry point for retinoid-naive skin.
Vitamin C
OTCAntioxidant + brightening. L-ascorbic acid is the most studied form.
Niacinamide
OTCBarrier support, oil control, and hyperpigmentation in one ingredient.
Hyaluronic Acid
OTCHumectant. Draws water into the skin. Works at multiple molecular weights.
Azelaic Acid
OTC / RxDual OTC/Rx. Strong evidence for rosacea and post-inflammatory hyperpigmentation.
Salicylic Acid
OTCBHA exfoliant. Penetrates follicles. Best studied ingredient for acne-prone skin.
What the Evidence Shows
50+ yrs
Tretinoin clinical history
Tretinoin has been studied in peer-reviewed literature since the 1970s. It is the most evidence-backed topical retinoid for acne and photoaging, with hundreds of randomized controlled trials supporting its use.
0.025%
Lowest effective tretinoin dose
Clinical studies show 0.025% tretinoin produces measurable collagen stimulation and acne clearance. Higher concentrations (0.05%, 0.1%) increase efficacy with proportionally higher irritation rates.
~12 wks
Time to see tretinoin results
Most clinical trials show statistically significant improvement in acne and skin texture at the 12-week mark. Purging (initial breakout worsening) is normal in weeks 2-6 and resolves with continued use.
Telehealth for Prescription Actives
Tretinoin and high-strength azelaic acid require a prescription in the US. Telehealth platforms connect patients with licensed providers who can prescribe these actives online, often at lower cost than an in-person dermatologist visit.
Common Questions
What are skincare actives?
Skincare actives are ingredients with a measurable, documented effect on skin biology. Common actives include retinoids (tretinoin, retinol), chemical exfoliants (AHAs, BHAs), antioxidants (vitamin C), and skin-brightening agents (niacinamide, azelaic acid). The term distinguishes them from inert ingredients like emollients and occlusives.
What is the difference between tretinoin and retinol?
Tretinoin is a prescription retinoid that binds directly to retinoic acid receptors in skin cells. Retinol is an OTC precursor that the skin converts to retinoic acid through a two-step process. Tretinoin is significantly more potent at equivalent concentrations but requires a licensed prescriber. Retinol is widely available without a prescription.
Can you use vitamin C and niacinamide together?
Yes. The concern that vitamin C and niacinamide form niacin (which causes flushing) has not been supported by clinical evidence at typical cosmetic use concentrations. Most dermatologists now consider the two safe to use together. The original concern was based on high-temperature, high-concentration lab conditions, not skin application.
What is the correct order to apply skincare actives?
General order: cleanser, then pH-dependent actives (vitamin C, AHAs, BHAs) at lower pH, then water-based serums, then moisturizer, then SPF (AM only). Retinoids are typically applied after moisturizer or sandwiched between moisturizer layers to reduce irritation. Actives with conflicting pH requirements (like vitamin C and niacinamide) can be applied at different times of day.