The Top 5 Soap Allergens That Trigger Dermatitis

What exactly is dermatitis? It's a symptom, not a standalone disease, and can refer to a variety of skin conditions. Dermatitis is any skin inflammation that results in redness, itching, scaling, or tiny fluid-filled blisters. It can stem from numerous causes, including fungal infections or fleas, but allergic contact dermatitis occurs when an allergy enters through the skin, causing inflammation. Similar to food allergies, these substances are typically harmless to non-allergic individuals, but plants like poison ivy can cause contact dermatitis in many people. Interestingly, the most common contact allergen isn’t a plant—it's nickel [source: Kunin].

The fastest way to trigger allergic contact dermatitis is by applying an allergen directly to your skin. A common product we use daily is soap. Ironically, this product meant to cleanse the skin could actually cause discomfort and irritation. Let's explore the five most frequent soap allergens that cause dermatitis.

5: Sodium Lauryl Sulfate

Sodium lauryl sulfate (SLS) is a widely used ingredient in soaps and shampoos. As a detergent, it excels at breaking down oil and grease, and it's the compound responsible for the frothy lather when you rub soap on your skin.

How does SLS lead to contact dermatitis? A common misconception is that the natural oils on our skin are dirty, but they actually serve an important protective role. While SLS is effective at dissolving oils and dirt, it also strips away the essential oil layer that prevents skin from drying out. Although SLS isn’t technically an allergen (since it doesn’t trigger an immune system response), it can contribute to contact dermatitis and worsen eczema by disrupting the skin’s natural barrier. This disruption allows other allergens to penetrate the skin, leading to reactions to substances that may not have caused issues before.

If you're struggling with dry, itchy skin, check your soap for sodium lauryl sulfate. You can also find it in products like toothpaste and bubble bath—essentially, anything that foams up to help clean.

4: Fragrance

Fragrance in soap might seem vague, but unfortunately, that's the reality. The beauty industry is highly competitive, and companies often keep the ingredients behind their signature scents a closely guarded secret. When you see 'fragrance' listed on a skincare product, it's a complex blend of esters, ketones, aldehydes, amines, and other substances. This makes fragrance allergy testing challenging, especially in North America, where the exact ingredients in most fragrances are not disclosed.

Although fragrance doesn't aid in skin cleansing, it remains one of the most common contact allergens in soaps. Additionally, fragrance allergens are present in almost every cosmetic product that isn't labeled as 'fragrance-free.' Since the cosmetics industry is mainly self-regulated in the U.S. and is secretive about its formulas, it's estimated that anywhere from 15 percent to nearly all cosmetic products contain fragrance allergens used for skin patch testing [source: Storrs].

3: Coconut Diethanolamide

While allergic reactions to eating coconut are rare, it's fairly common to have a reaction from simply touching them. You might assume that ingesting something would trigger a stronger reaction than something just touching the skin, but coconuts are an exception. They’re included in many skincare products due to their pleasant scent and their moisturizing and softening properties.

Coconuts can also be processed into coconut diethanolamide, a detergent used to create a stable lather in soaps. Like sodium lauryl sulfate (SLS), coconut diethanolamide can strip away the skin’s natural oily barrier, drying it out. However, some individuals experience more severe allergic reactions to it. Since coconut diethanolamide is commonly found in skincare items like barrier creams and hand protection foams, it can sensitize users quickly. Reactions can start within two to three months of use, whereas regular rinse-off soaps may take five to seven years to cause similar issues [source: Duffill]. Check product labels for coconut diethanolamide, which might also be listed as coconut oil acid, cocamide DEA, ninol, witcamide, or calamide.

2: Paraben

Paraben is a type of ester, both naturally occurring and synthetically produced. It is commonly used as a preservative and typically appears toward the bottom of ingredient lists in products like shampoos, soaps, toothpaste, and deodorants. While allergic reactions to paraben are relatively uncommon despite its widespread use, the presence of different parabens in the same product can increase the likelihood of an allergic response.

A notable point about parabens is that a 2004 study in the UK found traces of methylparaben in breast cancer tumor biopsies, suggesting a link to breast cancer [source: Yarosh]. Although additional studies have not proven any conclusive connection between parabens and cancer, many consumers remain cautious, preferring to avoid potential risks. Regardless of the uncertainty surrounding parabens' cancer-related claims, many cosmetic brands have adapted by offering a broad range of paraben-free products.

Parabens go by numerous chemical aliases, so if you suspect an allergy to paraben, inspect your soap and medicine cabinet for anything labeled with paraben or parahydroxybenzoic acid.

1: Balsam of Peru

Balsam of Peru, also known as myroxylon, is a sticky resin that has a fragrance reminiscent of vanilla and cinnamon. It is used in soaps, perfumes, and shampoos for both its scent and its fixative qualities, which slow down the rate at which the fragrance evaporates. Balsam of Peru can also be found in certain medications and foods, making appearances in products like calamine lotion, cough syrup, and even cola.

Cinnamein, a well-established allergen, comprises 60 to 70 percent of balsam of Peru, with the remaining 30 to 40 percent consisting of unidentified resins, any of which could trigger an allergic reaction. It's one of the most common causes of contact dermatitis, and approximately half of individuals with fragrance allergies react to balsam of Peru. The typical symptom of skin exposure is hand eczema, while consuming it may result in rashes around the mouth [source: Duffill].