The last time I tried two new skincare products at once, my face was on fire. Red, swollen, the lot. And the worst part? I couldn't tell you which of the two did it (so I went through all of that and learned nothing at all).
That's why I patch test now. Every single time, its dull, I know.
How do you patch test skincare if you have sensitive skin?
Put a little of the new product on your inner arm for a couple of days. Nothing happening? Move it to your jaw for a couple more. Jaw still happy after that, and it can go on your face. Then give it a fortnight before you decide whether it's doing anything, unless it stings, because stinging means stop.
About a week of waiting, all in. It's saved me more misery than any single product ever has.
Why I only add one thing at a time
I used to spend hundreds on skincare, buying whatever the label promised or whatever somebody online swore by, and the whole lot went on my face together. I tried the ten step routine as well. With sensitive skin every extra product is one more suspect when your face kicks off, and once you've got nine things on you're guessing.
So my routine is four steps now and I add one new thing to it, never two. When something does go wrong I know exactly what to blame. The whole routine is written up in Skincare for Sensitive Skin: The Short Routine That Works, along with the two toners and two moisturisers I keep going back to.
If it stings, it comes off
A new product can take a couple of weeks to show you what it's doing, so patience is fine. Stinging is different. It isn't purging and your skin isn't getting used to it (whatever the internet says). It comes off and it doesn't go back on.
What I check before it even gets near my arm
The label. Fragrance is the commonest cause of contact reactions in skincare, and it's in there for your nose, not your face. Watch "unscented" as well, because that can mean a masking fragrance has been added to cover the smell of the base. Fragrance free is the one you want.
If your face goes red as well as reactive, that's a slightly different job. I've done a separate write up on the best cream for rosacea UK, for the Boots and Superdrug side of it.
Quick answers
How long should I patch test for?
A couple of days on your inner arm, then a couple more on your jaw. Roughly a week.
How long before I know if a new product works?
Give it a fortnight, unless it stings. Stinging means stop straight away.
Can I patch test two products at the same time?
I wouldn't. One of them reacts and you won't know which, and you're back to the start.