Syndet Cleansers

Syndets (“synthetic detergents”) are cleansers made from synthetic surfactants instead of fatty-acid soap. Soap is made by saponifying fats with alkali and typically has a pH of 8.5–11.0; syndets are usually 5.5–7.0, overlapping with healthy skin surface pH of about 4.0–6.0 (Mijaljica et al., Molecules 2022). Some are acidified with lactic or citric acid. Alkaline soap can raise skin pH by about 3 units for 90 minutes, whereas syndets alter the acid mantle less and for a shorter time (Kumar & Das 2023; Panther & Jacob 2015). For a toddler with eczema, where Skin pH is already raised, that difference is the main argument for a syndet over soap when some cleansing is needed.

Syndet Cleansers [relates] Skin pH Syndet Cleansers [relates] Soap Substitutes

Barrier effects. In laboratory and volunteer studies, repeated soap washing damaged both protein and lipid regions of the stratum corneum, lifted surface cells and raised Transepidermal Water Loss; syndet-washed skin kept “well-conserved protein and lipid regions” (Mijaljica 2022). For eczema, the review notes that high-pH soap “can aggravate the skin, leading to loss of intracellular lipids” and recommends “mildly acidified syndets”. It also stresses that infant and child skin keeps maturing for several years, so children need a mild cleanser. A 28-day study of syndet bars in 50 people with mild AD (Solodkin 2006, Cutis) found them compatible with treatment. Evidence is mechanistic or from small industry-linked studies; no RCT has compared cleanser pH on eczema outcomes in toddlers.

Syndet Cleansers [prevents] Skin Barrier Dysfunction Sodium Lauryl Sulfate [relates] Syndet Cleansers

Labels don’t tell you the pH. Khan et al. (2024) measured 250 US cleansers. All 37 soaps were highly alkaline. Of 199 liquid syndets, 84.9% were acidic and 11.1% neutral, but none of 14 syndet bars was acidic (6 neutral, 8 alkaline). Only 15% of syndets stated their pH, and products labelled “balanced” ranged from acidic to alkaline. “Syndet” also does not mean gentle: Sodium Lauryl Sulfate is a synthetic surfactant and a known irritant. UK guidance prefers using the child’s leave-on emollient as a wash (Soap Substitutes); the American Academy of Dermatology accepts limited use of neutral-to-low-pH, fragrance-free non-soap cleansers.

Fragrance on broken skin

Many baby washes are perfumed. Fragrance chemicals on inflamed toddler skin can cause or reveal Fragrance Allergy. Choose fragrance-free (not just “unscented”) products.

Syndet Cleansers [relates] Fragrance Allergy

Connections

• Skin pH — preserves the acid mantle compared with soap, source: Kumar & Das 2023
• Soap Substitutes — US alternative to UK leave-on-emollient wash; syndet liquids 84.9% acidic, bars none, source: Khan et al. 2024
• Transepidermal Water Loss — soap raises TEWL more than syndets, source: Mijaljica 2022
• Sodium Lauryl Sulfate — irritant anionic surfactant; not all syndets are mild, source: Mijaljica 2022
• American Academy of Dermatology — neutral/low-pH non-soap cleansers, source: AAD guideline (see Soap Substitutes)
• Fragrance Allergy — perfumed baby washes, source: NEA triggers page