The short version of this tip:
Introduce new products to your makeup or
skincare routine one at a time.
skincare routine one at a time.
Here's my explanation:
When you get home from shopping with big bag of new products in hand, no matter the brand or store it came from, you're eager to try it all out (and I don't blame you!). The problem with trying a variety of new products all at once is that if your skin does react with irritation and breakouts you won't know what caused it. Then you pretty much have to go by process of elimination and since your skin is already irritated it might take a while to figure it out.
It's best to use new products one at a time (meaning one new product per daily routine) so that if your skin does freak out, you'll know why immediately. I mainly apply this rule to products I use on my face, such as foundation, blush, concealer, powder, primer, moisturizer, cleansers, scrubs, etc. My eyes and lip area are not sensitive to products nor is my body but you can adjust this rule to your benefit.