First, figure out what you are keeping and what you are getting rid of:
-Start by looking up your products in the EWG Skin Deep Cosmetics Database. Throw out everything that is rated in the red category (7 and up). These products are considered a significant hazard to your health and should be discarded immediately.
-Besides products with high hazard ratings, it is up to you to decide how strict you want to be about where you draw the line. I personally won't use anything above a 2 (the highest green rating).
-However, at this point you really need to start looking at the ratings of the ingredients. Sometimes products are rated higher than they should be, because - for example - they list fragrance in their ingredients, which the database will rate as a hazard. If the company specifies that they use natural, phthalate free fragrance, then it's probably okay. Sometimes the database rates a product as a low hazard even though it has bad ingredients, like talc or parabens, two ingredients I choose to avoid all together.
-Compare lists of chemicals you want to avoid to the ingredients in your products. This "Dirty Thirty" list is a fantastic place to start. If you don't know what an ingredient is, look it up in the cosmetics database or google it. Beware that innocent sounding ingredients, such as Vitamin A, can acutally be quite toxic.
-Another consideration is nanoparticles, often found in cosmetics as Zinc Oxide and Titanium Dioxide. These ingredients are relatively safe when they are in their regular form, but are a significant health concern when they are nano sized. It's impossible to know whether a product contains nanoparticles or not from reading the label. This is probably the biggest thorn in my side in terms of discerning safety, because unless a company specifies that they don't use nanoparticles, there is no way of knowing. When in doubt, send an email to the company and ask.
Now that you know what you need to get rid of, here are three tips that should make it a little easier:
-Swap products on makeupalley.com. I've gotten some brushes and bareMinerals products through this website, and it's a way of getting rid of products without feeling wasteful.
-If your friends ask for them, give your products away, while warning them about their hazardous ingredients. I know this sounds bad, because you are not using the products anymore because of the health hazard. However, I have friends who I've tried to talk to about this issue to over and over, and they still have no interest in changing. So it really doesn't make a difference if they rummage through my throw away pile.
-Just Throw. It. In. The. Trash. You'll be fine. Think about that awesome new product you bought that has only ingredients that you trust. You want everything in your collection to hold up to this standard.