New bottle? Arm first.
Every new product earns its way to your face via your inner forearm. Start a test below and we'll build the check schedule for you — 15 minutes, 24, 48 and 72 hours, day 7 — log what you see at each check, and call it: pass, proceed with care, or stop.
The protocol, in five moves
What dermatologists actually mean by "patch test it"- 1 Pick one spot and stick to it. Inner forearm or behind the ear. It has to be the exact same patch of skin every application — moving around resets the clock on delayed reactions.
- 2 Apply a small amount, once or twice daily. A pea-sized dab or less, for 7–10 days if it's a leave-on product. Rinse-off products get used like real life: apply, wait five minutes, rinse. Prefer a one-and-done approach? A single application kept under a bandage for 48 hours mimics how dermatologists occlude a test.
- 3 Then leave it alone. Don't wash the area right after applying — the product needs hours of skin contact to reveal anything. No scrubbing, no other products on that spot.
- 4 Check on a schedule, not on a whim. 15 minutes catches immediate stinging or hives; 24, 48 and 72 hours plus a day-7 look catch the slow burners. Contact allergy routinely shows up at 48–96 hours — a single early check misses it entirely.
- 5 Graduate to the jawline. Only after the arm passes. Face-adjacent skin is more reactive, so give the jawline 2–3 calm days before the product joins your full routine — and introduce one new product at a time.
Saved only on this device — and browsers erase site data. A history clear, a private window, or Safari's automatic deletion after seven days without a visit will take this log with it. The fix is a free DermApproved account: it backs this up automatically and puts it on every device you sign in to — details in how storage works.
- Natural & BotanicalHeartleaf Went Mainstream in Two Years. The Human Evidence Did Not Keep Up.The soothing plant on every K-beauty label has real anti-inflammatory pharmacology — and one human trial, in which it was one of four herbs in the same bottle.
- How We RateWe Could Publish a Pore-Clogging Score Tomorrow. We Won't.It would be the most-clicked number on this site and one of the least defensible — because the data underneath it was never designed to grade a finished product.
- Building a RoutineYou Changed Four Things and Learned NothingA routine is a system with load-bearing parts, and swapping several at once produces a result you cannot attribute to any of them — which is why most people's skincare knowledge never accumulates.
- Skin Barrier RepairThe Repair Routine Feels Like Doing Nothing. That Is Why People Abandon It.A wrecked barrier is the most common self-inflicted skin condition and the one with the clearest fix — the difficulty is that the routine which caused it feels productive and the one that repairs it feels like giving up.
Why a log beats winging it
The way dermatology clinics run patch tests holds a lesson for your bathroom counter: reactions are read on a schedule, at multiple timepoints, because contact allergy is slow. A product can feel fine for two days and then light up at hour 72. When you start a test here, the tool builds that schedule for you — an immediate 15-minute check for instant stinging, then reads at 24, 48 and 72 hours, and a day-7 look for the late reactors. Each check gets logged on a simple four-step scale, from all-clear to swelling or spreading rash, and the countdown on each active test tells you when the next read is due.
The verdict follows the readings, not vibes. Clear at every check through the final read is a pass — with jawline instructions for the graduation lap. Mild redness or dryness that settles earns a caution and an ease-in plan. Itching, burning, swelling, or a spreading rash ends the test on the spot with a clear instruction: stop, wash the area, and see a board-certified dermatologist if it doesn't settle. Everything lives on this device — no account, nothing uploaded. And a note worth repeating: this is an educational tool, not a diagnosis. A home test can't detect every allergy; formal patch testing with standardized allergens, applied and read by a dermatologist, is the real thing.
Common questions
How do I patch test a new skincare product at home?
Apply a small amount to the same spot on your inner forearm or behind your ear once or twice a day for 7–10 days for anything that stays on your skin. Don’t wash the area right after applying, and check it at set intervals — 15 minutes, then 24, 48 and 72 hours, then day 7. If the arm stays calm, repeat the test along your jawline for a couple of days before using it on your whole face.
How long should you patch test a product before using it on your face?
Longer than most people think. Contact allergy is often delayed — reactions commonly surface at 48 to 96 hours, and sometimes as late as a week in. A single overnight test only rules out immediate irritation, which is why leave-on products deserve the full 7–10 days. Rinse-off products like cleansers need less contact time, so three days of checks is usually enough.
Where is the best place to patch test — on your face or your arm?
Start on the inner forearm or behind the ear, not your face. The forearm is easy to monitor and forgiving; the skin behind your ear is thinner and closer in behavior to facial skin, so it’s a good choice for products you’re nervous about. If either spot passes, the jawline is the right second stage — it’s face-adjacent but discreet if something goes wrong. Never debut a new product across your whole face.
What does a positive patch test reaction look like?
Redness that persists rather than fading, itching or burning at the test spot, dryness or flaking that wasn’t there before, and — in stronger reactions — swelling, small blisters, or a rash that spreads beyond where you applied the product. A reaction that spreads or blisters is your cue to stop immediately, wash the area gently, and see a board-certified dermatologist if it doesn’t settle within a couple of days.
Is tingling normal when trying new skincare like retinol or acids?
A brief, mild tingle that fades within a few minutes can be normal with exfoliating acids, vitamin C, and retinoids — these actives work at low pH or speed up cell turnover, and skin notices. What’s not normal: burning that builds instead of fading, stinging that lasts, itching, or redness that’s still there hours later. Those are reaction signs, not “it’s working.”