You've read the ingredient list three times, and you still don't know if that new serum will work with your retinol.

Most of us buy skincare the same way. We see something everyone loves, add it to a routine that's already full, and hope for the best. Then our skin stings, breaks out or does nothing at all, and we can't tell which product caused it.

I made this guide so you can stop guessing. As a pharmacologist, I've taken 32 of the ingredients you'll find on almost every label and explained each one in plain language: what it does, who it suits and how to use it well. Then I went further, because knowing what an ingredient does is only half the story. You also need to know how it behaves next to everything else on your shelf.

Inside the guide:

32 ingredient cards, from niacinamide and retinol to urea and hydroquinone
What to Mix Together: 9 pairings that work well in the same routine
What to Avoid Mixing Together: 8 combinations to keep apart, and how to split them up
Morning and Night Routines: where each ingredient belongs in your day
Best Ingredients for Your Concern: what to use for acne, dark spots, dryness, sensitivity, fine lines and oily skin
Honest notes on what the research does and doesn't support, so you know which trends to try carefully

This guide is for you if you want a routine that makes sense, you're tired of products that fight each other, or you want someone to explain the label without the marketing.

What you get: a 16-page digital PDF, delivered instantly to your inbox. Read it on your phone, or print it and keep it by your shelf. This is a digital product, so no physical copy will be shipped.

At $4.99, it costs less than a single sheet mask, and it will help you make better choices with every product you buy after it.

Written by Rayo Johnson, MSc Pharmacology, founder of Skin Science Hub. This guide is for education and does not replace advice from your doctor or dermatologist. Because this is a digital download, all sales are final and non-refundable.