Deciphering the back of a beauty bottle can be like trying to understand a foreign language sans interpreter. With the unpronounceable terms and mystery ingredients, it's easy to feel lost. Unfortunately, not knowing what you're putting on your skin and hair has risks: The FDA doesn't approve personal-care products, and many contain elements that may pose health problems. To make matters worse, it's not just the ingredients in isolation that pose a problem. "We don't know how things work together," says Anne Marie Fine, M.D., a Scottsdale, Arizona-based naturopathic skin specialist, "or what the total effect from all the products we use every day will be." While you can't expect to avoid the bad stuff completely, you can get good at scanning labels for red-flag terms. With Fine's help, we identified eight common questionable ingredients. Keep these on your hit list, and start choosing healthier products.

1. Disodium Laureth Sulfosuccinate (DLS)
What It Is
A chemical salt 

What it Does
Lowers water's surface tension, which lets products spread out and penetrate more easily; boosts foaming action

Why Avoid?
It can produce harmful byproducts such as 1,4- dioxane and ethylene oxide, two chemicals linked to cancer. 

2. Triethanolamine (TEA)
What It Is
A chemical compound derived from ammonia 

What It Does
Acts as a cleansing agent and foam booster; prevents products from separating

Why Avoid?
Research has linked TEA to certain cancers. Additionally, it's sometimes contaminated with nitrosamines, a class of suspected carcinogens. TEA also may irritate skin and mucous membranes.

3. Parabens (i.e., butyl-, methyl-, and propylparabens)
What They Are
Chemical preservatives used in up to 90 percent of cosmetics 

What They Do
Keep products from going bad

Why Avoid?
Ongoing studies suggest parabens may act like estrogen in the body, and estrogen exposure has been linked to breast cancer and hormone disruptions. 

4. Propylene Glycol
What It Is
A thick, clear alcohol 

What It Does
Helps the skin soak up moisture, thins out liquids, and enhances skin's absorption of other ingredients in the product

Why Avoid?
It may interfere with reproductive health. Additionally, because it helps other substances sink into skin, it becomes detrimental if the product contains irritants or toxins. 

5. Phenoxyethanol
What It Is: An oily liquid preservative made from phenol, a coal tar derivative 

What It Does: Prevents scents from rapidly evaporating; sometimes used as a fragrance

Why Avoid?
Japan restricts use of phenoxyethanol, which research has linked to both endocrine disruption and cancers. It may also cause skin and eye irritation. 

6. Imidazolidinyl Urea
What It Is: The most commonly used preservative after parabens 

What It Does: Extends a product's shelf life

Why Avoid?
A top cause of contact dermatitis, imidazolidinyl urea may also stress your immune system. Plus, when used with water, it can release formaldehyde, a toxic chemical. 

7. PEGs
What They Are
Polyethylene glycol or polyethylene, which are both chemicals derived from petroleum 

What They Do
Help prevent products from separating; also used as gelling and thickening agents

Why Avoid?
PEGs can be contaminated with 1,4-dioxane, a known carcinogen created during the manufacturing process. Certain PEGs may also cause hives and eczema and have been linked to kidney toxicity.

8. Petrolatum
What It Is
Petroleum jelly 

What It Does
Helps skin retain moisture, softens skin, and gives products a shiny, smooth texture

Why Avoid?
Petrolatum forms a film on your skin to prevent moisture from escaping. Unfortunately, that film also traps toxins under the skin (your largest organ) and keeps it from breathing properly. This can clog pores and interfere with skin's excretory function (i.e., sweating) and cell development.