It can be tempting to choose shampoos based on flashy advertising promises or recommendations from that friend who never seems to have a bad hair day. But however unglamorous it may seem, taking a thorough look at the shampoo ingredients will give you a better idea of what you need. There are a variety of chemicals and other ingredients that can harm your hair, and still others that can potentially threaten your overall health. Take note of a few key offenders, and the next time you're facing dozens of choices in the hair-care aisle, you'll be prepared instead of overwhelmed.
If you color your hair, either professionally or on your own, you should use a gentle, color-preserving shampoo. The sulfates and harsh chemicals in some anti-dandruff or clarifying formulas can strip away your hard-won hair color. A sulfate is a salt of sulphuric acid, and sodium lauryl sulphate and sodium laureth sulphate are two of the kinds most commonly found in shampoos. While they do dissolve dirt and boost foam, it should be a red flag that they're also found in paint stripper.
The same types of sulfates are also to be avoided if you have frizz-prone, curly, or kinky hair. Though sodium lauryl sulfate and sodium laureth sulfate are both non-carcinogenic and do not come with any truly dangerous health risks, they can leave your hair frizzy and dry. If you already straighten your hair frequently, the drying, frizzy effects can be very potent, damaging your ends in particular and eventually causing breakage.
DEA (diethanolamine) and DEA compounds are used to make products like shampoos, cleansers and moisturizers creamy or sudsy. Cocamide and lauramide DEA are the main types found in shampoos. Minimal use of products containing DEA and its compounds may result in mild eye and skin irritation, but recent research suggests that prolonged exposure can cause much more serious problems, even cancer. By reacting with nitrites found in cosmetics as anti-corrosive agents, DEA compounds can potentially form nitrosamines, which the International Agency for Research on Cancer classifies as a possible human carcinogen. Despite its bacteria-busting properties, formaldehyde, an occasional shampoo ingredient, is also a known carcinogen that can irritate your skin, eyes and respiratory system.
The chemical compound isopropyl alcohol is derived from petroleum and is behind the oil-busting effects promised by many shampoos. Unfortunately, it's also commonly found in wood finish and shellac. In general, alcohol-based ingredients are also extremely drying and strip hair of its natural oils and moisture, leading to breakage and hair loss. Propylene glycol is another damage-inducing ingredient. Though it's a detergent that helps your hair look clean and fresh in the short term, after continual use it breaks down proteins that keep your hair looking healthy, hydrated and shiny. It can also leave your skin and eyes puffy and irritated.