Encyclopedia · surfactant
Decyl glucoside
A plant-derived mild cleanser marketed as ultra-gentle, but its best-documented concern is a rising rate of contact allergy.
What it is
Decyl glucoside is made from glucose (usually from corn or wheat) and decyl alcohol from coconut or palm. It appears in sulfate-free, baby and "natural" shampoos, often with a co-surfactant, because on its own it cleans weakly and foams softly.
How it works
Non-ionic head groups bind water by hydrogen bonds instead of charge, giving mild micelles. Compared with anionics, non-ionics generally extract less skin and hair lipid, though direct hair data on this ingredient are limited (Thompson 2023; Shaw 1979, a class-level comparison).
What the studies show
- In a 19-year patch-test cohort of 11,842 people, 30 reacted to alkyl glucosides. The causal products were shampoos (12), skin cleansers (12), sunscreens (5) and skin-care products (4), and 16 patients had multiple contact allergies (Gijbels 2014).
- A review noted alkyl glucosides were assumed to be low in irritancy and allergenicity, but cases of allergic contact dermatitis have accumulated since the early 2000s. Sensitisation to decyl glucoside is rising in North American data, and cross-reactions are common but not automatic (Alfalah 2017).
- A 2026 review found alkyl glucosides (mainly decyl, lauryl, cetearyl and coco-glucoside) have low irritation potential but can cause contact sensitisation (de Groot 2026).
These data concern allergy, not cleaning or hair outcomes. We found no hair-specific human trial for this ingredient, so the direct evidence is weak.
Side effects and safety
Irritation is low, but it is a recognised contact allergen. Cross-reactivity with other glucosides is common (Alfalah 2017). If a "gentle" shampoo makes your scalp itch, check the label for glucosides and consider a patch test.
Bottom line
Reasonable for dry or sensitive scalps without a known allergy, and best avoided if you have reacted to glucosides. Because it is a weak cleanser, oily scalps and heavy styling products may need a stronger primary surfactant. How common sensitisation is in the general population is unknown, since most data come from patients already referred for patch testing.
Studies 5
Gijbels D et al. Allergic contact dermatitis caused by alkyl glucosides. 2014
Result: Causal products were shampoos (12), skin cleansers (12), sunscreens (5) and skin-care products (4); 16 patients had multiple contact allergies.
Read the study ↗Alfalah M et al. Alkyl Glucosides. 2017
Result: Alkyl glucosides were assumed low in irritancy and allergenicity, but cases of allergic contact dermatitis have accumulated since the early 2000s; sensitisation to decyl glucoside is rising in North American data; cross-reactions are common but not automatic.
Read the study ↗de Groot AC. Contact Allergy to Alkyl Glucosides: A Review-Part 1. 2026
Result: Alkyl glucosides (mainly decyl, lauryl, cetearyl and coco-glucoside) have low irritation potential but can induce contact sensitisation.
Read the study ↗Thompson CJ, Ainger N, Starck P, Mykhaylyk OO, Ryan AJ. Shampoo Science: A Review of the Physiochemical Processes behind the Function of a Shampoo. Macromol Chem Phys. 2023
Result: Reviews how surfactants lift soil from hair (roll-up, emulsification, solubilization), why shampoos pair a primary anionic with an amphoteric co-surfactant, and states that foaming does not affect cleaning. Two authors were from Unilever R&D.
Read the study ↗Shaw DA. Hair lipid and surfactants. Extraction of lipid by surfactants and lack of effect of shampooing on rate of re-fatting of hair. Int J Cosmet Sci. 1979
Result: Changing shampoo frequency from once to three times a week had no significant effect on how fast hair re-fatted.
Read the study ↗Related
- Coco-glucosideA coconut-derived mild cleanser that is a staple of sulfate-free shampoos, with the same contact-allergy caveat as decyl glucoside.
- Lauryl glucosideA 12-carbon alkyl glucoside that foams a little better than decyl glucoside and carries the same class contact-allergy profile.
- Sodium cocoyl glutamateAn amino-acid-based cleanser that was among the best-tolerated surfactants in a 105-patient patch-test study, with no scalp or hair trials yet.
- Cocamidopropyl betaineThe most common helper surfactant in shampoo, which makes sulfate cleansers gentler, thicker and foamier, and a rare cause of scalp allergy that usually comes from manufacturing impurities.