Top 5 Allergens in Soaps That Cause Dermatitis

This bar of soap may look harmless, but it could be packed with allergens that can cause dermatitis.
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What is dermatitis? Dermatitis is a symptom, not a disease, and the word can apply to a wide range of skin conditions. Essentially, dermatitis is any inflammation of the skin that leads to redness, scaling, itching or tiny fluid-filled blisters. Dermatitis can have any number of causes, from fungal infection to fleas, but allergic contact dermatitis occurs when our bodies take in an allergy through our skin and, as a result, become inflamed. Like food allergies, most of these substances are harmless when ingested by people who aren't allergic, but there are also plants (like poison ivy) that produce contact dermatitis in a majority of the population. Oddly, the most common contact allergen isn't even a plant -- it's nickel [source: Kunin].

The quickest way to develop allergic contact dermatitis is by rubbing something you're allergic to on your bare skin. Something we rub on our skin on a regular basis is soap. Ironically, a product that's supposed to cleanse your skin can end up causing you a lot of pain and aggravation. We'll take a look at five of the most common allergens in soaps that cause dermatitis.


5: Sodium Lauryl Sulfate

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.

4: Fragrance

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].


3: Coconut Diethanolamide

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.


2: Paraben

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.

1: Balsam of Peru

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].


Allergens In Soap FAQ

What are irritants?
Irritants are substances or ingredients that irritate the skin. Five of the most common irritants in soap are sodium lauryl sulfate, fragrances, coconut diethanolamide, parabens, and balsam of Peru.
Can you be allergic to soap?
Yes, certain ingredients that are commonly used in soap can trigger allergies. Contact dermatitis can appear as red, itchy, inflamed skin and is caused by direct contact with a substance that you're allergic to.
What soap do dermatologists recommend?
Dermatologists generally suggest gentle, fragrance-free soaps. Recommended bar soap and cleanser brands include Dove, Neutrogena, Aquaphor, Method, Cetaphil, and CeraVe.
How long does it take for an allergic reaction to soap to go away?
You may not notice symptoms until 12 to 72 hours after exposure to the irritant. If you continue to expose your skin to the irritant, then symptoms will worsen, not improve. Ultimately, it may take a few hours to a few days to disappear.
How do you know if you're allergic to a soap?
If the skin on your hands becomes inflamed, red, scaly, and itchy, you might be allergic to your hand soap, or more likely, one ingredient in it. Stop using it and switch to another brand for a period of time and see if symptoms subside.

Lots More Information

Related HowStuffworks Articles

  • Australasian Society of Clinical Immunology and Allergy. "Allergic Contact Dermatitis." Feb. 8, 2001. (Aug. 18, 2009)
  • Australasian Society of Clinical Immunology and Allergy. "Coconut allergy." July 2006. (Aug. 18, 2009)
  • Kunin, Audrey. "The DERMAdoctor Skinstruction Manual." Simon and Schuster. 2005.
  • Duffill, Mark. "Coconut diethanolamide allergy." New Zealand Dermatological Society. June 15, 2009. (Aug. 18, 2009)
  • Ngan, Vanessa. "Allergy to parabens." New Zealand Dermatological Society. June 15, 2009. (Aug. 17, 2009)
  • Ngan, Vanessa. "Balsam of Peru." New Zealand Dermatological Society. June 15, 2009. (Aug. 17, 2009)
  • Storrs, Frances J. "Allergen of the Year: Fragrance." Medscape Today. July 30, 2007. (Aug. 18, 2009)
  • U.S. Department of Health and Human Services. "Sodium Lauryl Sulfate (SLS)." Household Products Database. September 26, 2008. (Aug. 14, 2009)
  • Yarosh, Daniel. "The New Science of Perfect Skin." Broadway Books. 2008.