Sodium Lauryl Sulfate

Sodium lauryl sulfate (SLS, also spelt sulphate, or sodium dodecyl sulfate) is a cheap anionic detergent and foaming agent. It is in the emulsifying wax of Aqueous Cream, and it is widely used in toothpaste, shampoo, body wash and bubble bath. Tsang and Guy call it “a known skin irritant and a commonly used excipient in personal care and household products” (Br J Dermatol 2010). It is an irritant, not an allergen. It strips the skin’s surface lipids, so it harms everyone’s barrier somewhat, and harms the already leaky barrier of Atopic Dermatitis more (Skin Barrier Dysfunction). Like soap, surfactants raise Skin pH, which favours Staphylococcus aureus and barrier-damaging enzymes.

Sodium Lauryl Sulfate [part-of] Aqueous Cream Sodium Lauryl Sulfate [worsens] Skin Barrier Dysfunction Sodium Lauryl Sulfate [worsens] Skin pH Sodium Lauryl Sulfate [triggers] Atopic Dermatitis

Tsang & Guy 2010: aqueous cream thins the outer skin. At the University of Bath, six healthy volunteers applied Aqueous Cream BP (about 1% SLS) twice daily to one side of each forearm for 4 weeks. The other side was untreated. The outermost layer (stratum corneum) became 1.1 µm thinner on treated skin, a 12% loss (P=0.0015). Baseline Transepidermal Water Loss rose by 2.5 g/m²/h, a 20% rise (P<0.0001), and water loss rose faster when the skin was tape-stripped. The changes showed in 16 of 27 treated sites. The authors said this calls into question using the cream on eczema, where the barrier is already compromised. The volunteers did not have eczema and the study was small. Press coverage (BBC 2010) rounded the thinning to “about 10%“. It quoted a poll in which nine out of 10 GPs recommended aqueous cream for childhood eczema. The National Eczema Society called SLS “a fairly heavy duty detergent”.

Sodium Lauryl Sulfate [causes] Transepidermal Water Loss Sodium Lauryl Sulfate [worsens] Skin Barrier Dysfunction

Regulator response in children. In 2013 the MHRA warned that aqueous cream used as a leave-on emollient can cause stinging, burning, itching and redness, especially in children. It named SLS as the likely cause. In an audit of 100 children (Cork 2003), aqueous cream caused an immediate reaction within 20 minutes in 56% of exposures, compared with 18% for other emollients. The advice was to stop and switch to an SLS-free emollient. The MHRA and NICE still allow aqueous cream as a wash, but dermatology nurse specialists advise against it even as a wash (Nursing in Practice) (see the conflict in Aqueous Cream). In South Africa public clinics still mainly issue aqueous cream. The national algorithm limits it to a wash product only, never leave-on (South African Eczema Guidance). In Hard Water more surfactant residue stays on the skin after washing (Jabbar-Lopez 2021), which may help explain the link between hard water and eczema.

MHRA [opposes] Sodium Lauryl Sulfate Hard Water [worsens] Sodium Lauryl Sulfate South African Eczema Guidance [regulates] Aqueous Cream

Toothpaste, bubble bath and other everyday sources. SLS is a common foaming agent in toothpaste. DermNet says it can cause irritant contact dermatitis, especially of the skin around the mouth, and it may make mouth ulcers more frequent (evidence mixed). For a toddler with eczema or Perioral Dermatitis around the mouth, toothpaste froth on the chin and lips is one possible irritant, alongside saliva (Drool Dermatitis). Allergy UK advises people with eczema to avoid perfumed shower gels and bubble bath and to wash with an emollient soap substitute instead. These foaming products usually rely on SLS or related surfactants, so the practical rule is to choose SLS-free, fragrance-free washes, or Syndet Cleansers at a skin-friendly pH. One parent on r/toddlertips reported a dermatologist advising against fluoridated toothpaste for a 2-year-old’s perioral rash (evidence: anecdotal). No trial located has tested SLS-free toothpaste in toddler eczema.

Sodium Lauryl Sulfate [triggers] Perioral Dermatitis Soap Substitutes [opposes] Sodium Lauryl Sulfate Syndet Cleansers [relates] Sodium Lauryl Sulfate

Stinging leave-on products

Do not use SLS-containing aqueous cream as a toddler’s leave-on moisturiser, and avoid bubble bath on eczema. If a cream or wash stings and does not settle, stop it and switch to an SLS-free, fragrance-free product.

Connections

• Emollient Therapy — irritant to avoid in emollients, source: MHRA 2013
• Aqueous Cream — linked from aqueous cream note, source: MHRA 2013
• Skin Barrier Dysfunction — surfactant raises skin pH and damages barrier; deposits more under hard water, source: Elias & Wakefield 2011; Jabbar-Lopez 2021
• MHRA — cited in 2013 aqueous cream warning, source: MHRA 2013
• Hard Water — more surfactant residue deposited in hard water, source: Jabbar-Lopez 2021
• Soap Substitutes — avoid SLS-containing washes (aqueous cream), source: MHRA 2013; NES
• Transepidermal Water Loss — aqueous cream raised TEWL 20% in 4 weeks, source: Tsang & Guy 2010
• Perioral Dermatitis — SLS toothpaste irritates perioral skin, source: DermNet
• Skin pH — surfactants raise skin pH, source: Kumar & Das 2023
• South African Eczema Guidance — aqueous cream wash-only in SA algorithm, source: Kannenberg 2020
• Syndet Cleansers — milder synthetic-detergent alternative, source: Kumar & Das 2023