Top 5 Allergens in Soaps That Cause Dermatitis

Sodium lauryl sulfate (SLS) is a common ingredient found in soaps and shampoos. SLS is a detergent, which means it does a good job of breaking up oil and grease. It's also the substance that makes soap get frothy when you rub it on your body.

So how does SLS contribute to contact dermatitis? One common skin-care myth is that the oil on our bodies is dirty, but the truth is that we need a reasonable amount of it for protection. While SLS is useful for breaking up greasy foreign substances, it also breaks up the layer of oil that keeps our skin from drying out. And while it's not technically an allergen because it doesn't provoke a reaction from the immune system, SLS can cause contact dermatitis and aggravate eczema by weakening that oily barrier on our skin. This means that SLS can usher other allergic elements into your body. After repeated exposure to these elements, you may develop reactions to things you weren't allergic to before.

If you're having a problem with dry, itchy skin, check your soap for sodium lauryl sulfate. It also appears in toothpaste and bubble bath -- pretty much anything that foams up to get you clean.

Wait, fragrance? Isn't that a little general? Unfortunately, yes. The soap market is a cutthroat place, and companies are cagey about revealing the ingredients that make their formulas smell just right. When you see fragrance listed as an ingredient on a skin care product, you're looking at a top-secret mix of esters, ketones, aldehydes, amines and more. This makes it difficult to construct allergy tests for fragrance because, in North America in particular, we don't even know what the ingredients in most fragrances are.

Even though fragrance doesn't actually contribute to skin cleansing, it's one of the most common contact allergens in soap. Furthermore, fragrance allergens are found in just about any cosmetic product that doesn't carry a "fragrance-free" label. And because the cosmetics industry (which is largely self-regulated in the United States) is pretty secretive about its formulas, the estimated range of cosmetic products that contain the fragrance allergens used for skin patch testing is anywhere from 15 percent to all of them [source: Storrs].

While allergic reactions to ingesting coconut are rare, it's not uncommon to have an allergic reaction to touching them. You'd think that it would be harder for your body to deal with things you put in your mouth than stuff that just touches your skin, but coconuts are an exception. What's more, they show up in all kinds of skin care products, both for their delicious scent and their ability to moisturize and soften skin.

However, coconuts can also be made into coconut diethanolamide, a detergent that helps create a stable lather when you're washing with soap. Like sodium lauryl sulfate (SLS), coconut diethanolamide can break down skin's oily barrier layer and dry it out, but certain people develop more intense allergic reactions to it. Since coconut diethanolamide is a common ingredient in skin care products such as barrier creams and hand protection foams, sensitizing can happen rapidly. You may begin to develop reactions after using a product for two or three months. Regular rinse-off soaps, however, take much longer to produce a reaction -- more like five to seven years [source: Duffill]. Check ingredient lists for coconut diethanolamide, and be aware that it may be masquerading under such names as coconut oil acid, cocamide DEA, ninol, witcamide and calamide.

Paraben is both an industrially produced and naturally occurring ester. Used as a preservative, it's usually near the bottom of the ingredient list in shampoos, soaps, toothpaste and deodorant. Allergic reactions to it are relatively rare when you consider how common it is, but different types of parabens also often appear in the same product, increasing the chance of a reaction.

One thing that should be mentioned regarding parabens is that a 2004 study in the United Kingdom linked them to breast cancer after trace amounts of methylparaben were found in breast cancer tumor biopsies [source: Yarosh]. Although further research has produced no conclusive evidence that parabens cause cancer, many consumers are still worried, preferring to take a better-safe-than-sorry approach to skin care. Whether or not the claims about the dangers of parabens are true, cosmetics companies have compensated for the backlash and now offer a wide variety of paraben-free products.

Parabens go by a long list of chemical pseudonyms, so if you think you're allergic to paraben, check your soaps and medicine cabinet for anything with paraben or parahydroxybenzoic in it.

Balsam of Peru, also known as myroxylon, is a sticky sap that smells like vanilla and cinnamon. It's used as an ingredient in soaps, perfumes and shampoos both for its smell and for its quality as a fixative, which helps slow down evaporation. It's also added to certain medications and food, showing up in everything from calamine lotion to cough medicine and cola.

Cinnamein, a well-documented potential allergen, makes up between 60 and 70 percent of balsam of Peru, while the other 30 to 40 percent is made of unknown resins, any of which can provoke an allergic reaction. It's one of the most common causes of contact dermatitis, and about half of people who have a fragrance allergy have a reaction to balsam of Peru. The most common symptom is hand eczema in the case of skin contact, and when it's consumed, rashes may form around the mouth [source: Duffill].