Soft, pre-washed 100% cotton is the safest default next to eczema-prone skin. What decides whether a fabric irritates is fibre diameter, how it handles moisture, and what was added to the cloth after weaving. Two pieces of standard advice have not held up: superfine merino below 18.5 microns reduced severity in a crossover trial, while silk therapeutic garments failed to beat standard care in a 300-child UK trial.
Fabric reaches a compromised barrier three ways: fibre ends stiff enough to press in and fire the nerve endings that carry itch, trapped heat and sweat, and the chemistry left in the cloth (dyes, finishing resins, detergent residue).
Fibre diameter is the number that matters
The itch a jumper causes is usually not an allergy. A 2017 review found no evidence that wool fibre is a cutaneous allergen, and rated lanolin contact dermatitis from modern wool garments as very unlikely (Zallmann et al, 2017). The trigger is mechanical: fibre diameters of 30 to 32 microns and above generate enough force to activate the C-fibre nerve endings that signal itch. Below that, the fibre end buckles instead of pressing in.
Much ordinary wool knitwear carries enough fibres above that threshold to prickle; superfine merino sits well below it. In the DESSINE crossover study, 39 children aged four weeks to three years with mild to moderate eczema wore superfine merino of 15.0 to 18.5 microns and cotton for six weeks each. Wool periods scored a mean objective SCORAD 7.6 points lower, 95% confidence interval 4.8 to 10.4 (Su et al, 2017). It was small, ran only in young children, and Australian Wool Innovation funded it and supplied the garments. Enough not to rule superfine merino out, not enough to prefer it to cotton.
Sweat, heat and the overnight itch
Sweating is one of the most common triggers of itch in eczema (Hong et al, 2011), and the mechanism is not simply wetness. Sweat carries salt and proteins that irritate a leaky barrier, and it only cools when it evaporates. Under polyester it stays liquid on the skin while the skin keeps heating.
Cotton and superfine wool absorb moisture into the fibre, pulling it off the surface. Polyester moves liquid along the outside of the fibre and needs airflow, which a duvet removes. Wicking sportswear is not sleepwear, and the difference feeds the itch-scratch cycle at the hours when scratching is unconscious. Bedding matters more than any garment because contact runs unbroken for seven or eight hours. Cotton sheets, a lighter summer duvet tog and a cooler bedroom do more than an expensive pillowcase, alongside the wider home environment work.
Silk, silver and therapeutic garments
The CLOTHES trial randomised 300 children aged 1 to 15 with moderate to severe eczema to sericin-free silk garments plus standard care, or standard care alone, for six months, with blinded nurses scoring the Eczema Area and Severity Index. The adjusted ratio of geometric means was 0.95 (95% CI 0.85 to 1.07, p = 0.43), and the authors concluded that silk clothing is unlikely to add benefit over standard care (Thomas et al, 2017). Cost per quality-adjusted life year came to £56,811, and at a willingness to pay of £30,000 the probability of cost-effectiveness was 12.13%.
Silver garments target Staphylococcus aureus colonisation instead. Gauger and colleagues found SCORAD fell 27.4% with silver-coated textiles against 16.3% with placebo cotton over two weeks, with no significant difference between groups. Fluhr and colleagues found silver-loaded seaweed garments cut colonisation in 10 participants against four on cotton at eight weeks (NIHR Health Technology Assessment, 2017). Both are small, short studies of a treated surface that laundering strips.
Dyes, finishes and washing
The fibre can be fine and the colour still a problem. Disperse dyes, used on polyester and other synthetics, are not chemically bonded to the fibre the way reactive dyes are to cotton, so they migrate out with sweat. Routine patch-test series put textile dye mix reactions at roughly 1.5% to 3.7%; in a Dutch cohort of 209 patients referred with suspected textile allergy it reached 13.9%, led by Disperse Orange 3 at 9.6% (Nijman et al, 2023). Permanent-press and crease-resistant finishes add formaldehyde-releasing resins bonded into the cloth.
Dye and finish are both surface-bound and partly water-soluble, which is why washing new clothes twice before wearing removes a share of each. Detergent works the other way, a residue that repeats its exposure every time you sweat into the cloth, and the NHS lists it alongside soap and some fabrics among the things to avoid where they make eczema worse (NHS, Atopic eczema: treatment). Run an extra rinse cycle, and skip fabric softener, which deposits a cationic film built to stay on the fibre.
Seams, labels and wrap garments
On inflamed skin the seam is often where the flare line falls: a stitched ridge presses harder than the cloth around it and moves with every step. Look for flat-lock seams, seam-free bodies and printed labels, not woven neck tags. Turning a garment inside out costs nothing.
Fit belongs to the same mechanism: loose garments rub less than tight ones over the elbow and knee creases where eczema concentrates. The deliberate exception is compression, where tubular bandage garments and cotton wrap suits are used in wet wrap therapy because a snug damp layer holds emollient against the skin and blocks overnight scratching.
What to wear, by situation
- Cold weather: lambswool over a cotton layer, never against skin. Superfine merino only where the label states 18.5 microns or finer.
- Exercise: change out of the wet layer promptly rather than picking a fabric to sit in.
- A rash tracing the outline of one garment: that garment, not the washing powder.
- A flare: the plainest cotton you own, worn loose, inside out if seams are raised.
References
- Zallmann M, et al. Debunking the myth of wool allergy. Acta Dermato-Venereologica, 2017. https://www.medicaljournals.se/acta/content/html/10.2340/00015555-2655
- Su JC, et al. Determining Effects of Superfine Sheep wool in INfantile Eczema (DESSINE). British Journal of Dermatology, 2017;177(1):125-133. https://academic.oup.com/bjd/article/177/1/125/6601946
- Thomas KS, et al. Silk garments plus standard care for treating eczema in children (CLOTHES Trial). PLOS Medicine, 2017. https://journals.plos.org/plosmedicine/article?id=10.1371%2Fjournal.pmed.1002280
- Thomas KS, et al. Randomised controlled trial of silk therapeutic garments for the management of atopic eczema in children: the CLOTHES trial. NIHR Health Technology Assessment, 2017. https://www.ncbi.nlm.nih.gov/books/NBK425574/
- Nijman L, et al. The prevalence and relevance of patch testing with textile dyes. Contact Dermatitis, 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10108160/
- Hong et al. Management of Itch in Atopic Dermatitis. Seminars in Cutaneous Medicine and Surgery, 2011. https://pmc.ncbi.nlm.nih.gov/articles/PMC3704137/
- NHS. Atopic eczema: treatment. https://www.nhs.uk/conditions/atopic-eczema/treatment/