You know how sometimes you run out of face cleanser, so you turn to whatever else is in your shower instead? (Hopefully we're not the only ones...) Or how, perhaps, you buy a toner, serum, etc. because your BFF loves it or it has pretty packaging-without checking out the ingredients? Well, you might want to be a bit more careful about what you're putting on your precious, beautiful face, both when it comes to products that are meant for other things (i.e. shampoo) and products that could contain substances that really aren't that great for your skin.

To help you determine the bad from the good, we got the scoop from celebrity facialist Joanna Vargas, founder of Joanna Vargas Salon and Skincare Collection, and Dr. Elizabeth Tanzi, co-director of the Washington Institute of Dermatologic Laser Surgery in Washington, DC. Here are the ingredients you need to beware of.

Retin A
Vargas warns that while this product is touted as an acne and anti-aging miracle, it must be used with caution as, "it thins the skin and can cause an enormous amount of sensitivity." Tanzi agrees, noting that those with dry skin have to be careful not to use retinols too aggressively.

Propylene Glycol
This substance is used to both absorb extra water and maintain moisture in various products, cosmetic and otherwise, but for our purposes, it's mainly found in shampoos, hair conditioners, and leave-in styling products. It's certainly not something you want to ever put on your face-even if you're just using a squirt of shampoo to scrub off your eye makeup really quickly, because it's toxic, Vargas says. "It's basically like using anti-freeze on your skin," she explains.

Sodium Lauryl Sulfate
Commonly found in cleansers, this compound is also used in car washes and engine degreasers. Yes, really. "It is so bad for you," Vargas says. "It can cause skin sensitivity, breathing problems and major damage to the immune system." Avoid, avoid, avoid!

Parabens
These preservatives are used in a lot of personal care products to extend their shelf life, Tanzi says. "People with sensitive skin should also avoid them because they can cause irritation," she says. "Besides being a possible allergy-causing preservative, there are questions about their safety as a whole when absorbed in high amounts in the body. They've been controversial because they can stimulate estrogen, so people are concerned with the risk of breast cancer and stimulating puberty in children." Yikes.

Shea Butter
Shea butter is an incredible moisturizer... for your body. Those with oily skin especially should avoid putting shea butter on their faces, as it can clog pores and make skin oilier.

Pure Vitamin E Oil
Tanzi notes that, despite its restorative benefits, this oil is another ingredient to avoid. "It can clog pores and some people actually can develop an itchy rash to it," she says.

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