Wrinkle

A wrinkle, also known as a rhytid, is a fold, ridge or crease in an otherwise smooth surface, such as on skin or fabric. Skin wrinkles typically appear as a result of ageing processes such as glycation,^[1] habitual sleeping positions,^[2] loss of body mass, sun damage,^[3] or temporarily, as the result of prolonged immersion in water. Age wrinkling in the skin is promoted by habitual facial expressions, aging, sun damage, smoking, poor hydration, and various other factors.^[4] In humans, it can also be prevented to some degree by avoiding excessive solar exposure and through diet (in particular through consumption of carotenoids, tocopherols and flavonoids, vitamins (A, C, D and E), essential omega-3-fatty acids, certain proteins and lactobacilli).^[5]

Skin

Causes for aging wrinkles

Development of facial wrinkles is a kind of fibrosis of the skin. Misrepair-accumulation aging theory suggests that wrinkles develop from incorrect repairs of injured elastic fibers and collagen fibers.^[6]^[7]^[8] Repeated extensions and compressions of the skin cause repeated injuries of extracellular fibers in derma. During the repairing process, some of the broken elastic fibers and collagen fibers are not regenerated and restored but replaced by altered fibers. When an elastic fiber is broken in an extended state, it may be replaced by a "long" collagen fiber. Accumulation of "long" collagen fibers makes part of the skin looser and stiffer, and as a consequence, a big fold of skin appears. When a "long" collagen is broken in a compressed state, it may be replaced by a "short" collagen fiber. The "shorter" collagen fibers will restrict the extension of "longer" fibers, and make the "long" fibers in a folding state permanently. A small fold, namely a permanent wrinkle, then appears.

Sleep wrinkles

Sleep wrinkles, also known as sleep lines or sleep creases, are facial wrinkles that form primarily from repeated mechanical compression, shear forces, and distortion of facial skin during sleep, especially in side or stomach sleeping positions.^[9] Unlike dynamic wrinkles caused by repeated facial muscle contractions (e.g., frown lines or crow's feet), sleep wrinkles result from external forces such as sustained pressure against a pillow surface and positional shifts that create lateral drag or folding of the skin.^[10] These forces can lead to temporary creases that become more permanent over time due to cumulative mechanical stress, reduced skin elasticity with aging, and potential disruption of collagen and elastic fibers in the dermis.^[9] The location of sleep wrinkles often corresponds to predictable patterns influenced by sleep position and facial anatomy, such as the superficial musculoaponeurotic system (SMAS).^[9] Common areas include the cheeks, nasolabial folds, and periorbital regions. Some sources suggest that pillowcase materials with lower surface friction (e.g., smooth fabrics like silk or satin) may reduce skin drag and shear compared to rougher materials like cotton, potentially slowing the progression of sleep wrinkles, though direct clinical evidence remains limited and mostly observational or from small-scale studies.^[11]^[12] Dermatologists note that reducing friction does not reverse existing wrinkles but may help mitigate an environmental contributor.^[13] Back sleeping is often recommended to minimize these effects, as it avoids direct facial compression against bedding.^[9]

Low-friction pillowcases

Low-friction pillowcases are designed to minimize skin shear and drag during sleep, potentially interrupting friction-related progression of sleep wrinkles. Common design elements include envelope closures to secure the pillow without zippers or buttons that could cause snags or discomfort, standard sizes such as 20x26 inches for conventional pillows to prevent shifting, and hypoallergenic certifications to resist allergens like dust mites and mold during extended facial contact.

Production techniques often involve weaving methods that interlace warp and weft yarns at right angles to create a uniform, smooth surface for consistent low resistance, and dyeing processes using water-soluble solutions enhanced by salts for even color distribution while avoiding harsh irritants. These methods help maintain low-friction properties and skin compatibility.

Commercially, silk-based low-friction pillowcases are offered by brands like YouthSecret (using engineered multi-layer textiles with lab-reported low coefficient of friction) and Blissy (using 22-momme mulberry silk), alongside satin options from Tyfitb and MR&HM. Pricing typically ranges from $20 to $100 per pillowcase, depending on size, material quality, and features, with such products gaining popularity since the late 2010s alongside skincare-focused bedding trends.^[14]

Customization options include tailored fits for sleep positions, such as curved designs for side sleepers to reduce fabric movement or standard shapes for back sleepers to ensure stability. Independent lab testing on some low-friction textiles (e.g., ASTM D1894) reports very low coefficients of friction, supporting reduced shear potential, though direct clinical evidence for wrinkle prevention remains limited and observational.^[15]

Water-immersion wrinkling

The wrinkles that occur in skin over prolonged exposure to water are sometimes referred to as pruney fingers or water aging. This is a temporary skin condition where the skin on the palms of the hand or feet becomes wrinkly. This wrinkling response may have imparted an evolutionary benefit by providing improved traction in wet conditions,^[16] and a better grasp of wet objects.^[17] These results were called into question by a 2014 study that failed to reproduce any improvement of handling wet objects with wrinkled fingertips.^[18] However, a 2021 study of gripping efficiency found that wrinkles decreased the force required to grip wet objects by 20%, supporting the traction hypothesis.^[19]

Prior to a 1935 study, the common explanation was based on water absorption in the keratin-laden epithelial skin when immersed in water,^[20] causing the skin to expand and resulting in a larger surface area, forcing it to wrinkle. Usually the tips of the fingers and toes are the first to wrinkle because of a thicker layer of keratin and an absence of hairs which secrete the protective oil called sebum.

In the 1935 study, however, Lewis and Pickering were studying patients with palsy of the median nerve when they discovered that skin wrinkling did not occur in the areas of the patients' skin normally innervated by the damaged nerve. This suggested that the nervous system plays an essential role in wrinkling, so the phenomenon could not be entirely explained simply by water absorption. Recent research shows that wrinkling is related to vasoconstriction.^[21]^[22] Water probably initiates the wrinkling process by altering the balance of electrolytes in the skin as it diffuses into the hands and soles via their many sweat ducts. This could alter the stability of the membranes of the many neurons that synapse on the many blood vessels underneath skin, causing them to fire more rapidly. Increased neuronal firing causes blood vessels to constrict, decreasing the amount of fluid underneath the skin. This decrease in fluid would cause a decrease in tension, causing the skin to become wrinkly.^[23]

This insight resulted in bedside tests for nerve damage and vasoconstriction. Wrinkling is often scored with immersion of the hands for 30 minutes in water or EMLA cream with measurements steps of 5 minutes, and counting the number of visible wrinkles in time. Not all healthy persons have finger wrinkling after immersion, so it would be safe to say that sympathetic function is preserved if finger wrinkling after immersion in water is observed, but if the fingers emerge smooth it cannot be assumed that there is a lesion to the autonomic supply or to the peripheral nerves of the hand.^[24]

Other animals with wrinkles

Examples of wrinkles can be found in various animal species that grow loose, excess skin, particularly when they are young. Several breeds of dog, such as the Pug and the Shar Pei, have been bred to exaggerate this trait. In dogs bred for fighting, this is the result of selection for loose skin, which confers a protective advantage.^[25]

Techniques for reducing the appearance of aging wrinkles

Retinoids

Retinoids, a class of natural and synthetic vitamin A analogues, are widely utilized for their anti-aging effects, specifically in the reduction of facial wrinkles and fine lines. Tretinoin (Retin-A) and tazarotene (Tazorac) are the only topical retinoids approved as medical agents for the treatment of wrinkles and fine lines from photodamage.^[26]^[27] Other retinoids, such as retinol, retinaldehyde, and retinyl palmitate, are commonly found in over-the-counter cosmeceuticals and have some evidence for reducing wrinkles and fine lines but are regulated as cosmetics rather than medicines.^[26]

Retinoids function by binding to retinoic acid receptors (RAR) and retinoid-X receptors (RXR), which promotes keratinocyte proliferation, increases epithelial cell turnover, stimulates collagen synthesis, and inhibits collagen degradation.^[26]^[27] Retinoids also appear to improve the epidermal barrier and reduce transepithelial water loss.^[26]

Glycosaminoglycans

Topical glycosaminoglycans supplements can help to provide temporary restoration of enzyme balance to slow or prevent matrix breakdown and consequent onset of wrinkle formation. Glycosaminoglycans (GAGs) are produced by the body to maintain structural integrity in tissues and to maintain fluid balance. Hyaluronic acid is a type of GAG that promotes collagen synthesis, repair, and hydration. GAGs serve as a natural moisturizer and lubricant between epidermal cells to inhibit the production of matrix metalloproteinases (MMPs).

Injectable fillers

Dermal fillers are injectable products frequently used to correct wrinkles, and other depressions in the skin. They are often a kind of soft tissue designed to enable injection into the skin for purposes of improving the appearance. The most common products are based on hyaluronic acid and calcium hydroxylapatite.

Neuromodulators

Botulinum toxin is a neurotoxin protein produced by the bacterium Clostridium botulinum. The neurotoxin treats wrinkles by immobilizing the muscles that cause wrinkles. It is not appropriate for the treatment of all wrinkles; it is indicated for the treatment of glabellar lines (between the eyebrows) in adults. Any other usage is not approved by the FDA and is considered off-label use.

Botox is a specific form of botulinum toxin manufactured by Allergan for both therapeutic and cosmetic use. Besides its cosmetic application, Botox is used in the treatment of other conditions including migraine headache and cervical dystonia (spasmodic torticollis) (a neuromuscular disorder involving the head and neck).^[28]

Dysport, manufactured by Ipsen, received FDA approval and is now used to treat cervical dystonia as well as glabellar lines in adults. In 2010, another form of botulinum toxin, one free of complexing proteins, became available to Americans. Xeomin received FDA approval for medical indications in 2010 and cosmetic indications in 2011.

Photorejuvenation

Laser resurfacing is an FDA-cleared skin resurfacing procedure in which lasers are used to improve the condition of the skin.^{[citation needed]} Two types of lasers are used to reduce the appearance of fine lines and wrinkles on the face; laser ablation, which removes thin layers of skin, and nonablative lasers that stimulate collagen production. Nonablative lasers are less effective than ablative ones, but they are less invasive, and recovery time is short. After the procedure people experience temporary redness, itching and swelling.

References

^ Danby, FW (Jul–Aug 2010). "Nutrition and aging skin: sugar and glycation". Clin Dermatol. 4. 28 (4): 409–411. doi:10.1016/j.clindermatol.2010.03.018. PMID 20620757.
^ American Academy of Dermatology. "Causes of Aging". AgingSkinNet. American Academy of Dermatology. Retrieved 5 March 2013.
^ Cosmetic Procedures for Wrinkles
^ Anderson, Laurence. 2006. Looking Good, the Australian guide to skin care, cosmetic medicine and cosmetic surgery. AMPCo. Sydney. ISBN 0-85557-044-X.
^ Schagen, S. K.; Zampeli, V. A.; Makrantonaki, E.; Zouboulis, C. C. (2012). "Discovering the link between nutrition and skin aging". Dermato-Endocrinology. 4 (3): 298–307. doi:10.4161/derm.22876. PMC 3583891. PMID 23467449.
^ Wang, Jicun; Michelitsch, Thomas; Wunderlin, Arne; Mahadeva, Ravi (2009). "Aging as a consequence of Misrepair—a novel theory of aging". arXiv:0904.0575 [q-bio.TO].
^ Wang-Michelitsch, Jicun; Michelitsch, Thomas (2015). "Aging as a process of accumulation of Misrepairs". arXiv:1503.07163 [q-bio.TO].
^ Wang-Michelitsch, Jicun; Michelitsch, Thomas (2015). "Tissue fibrosis: a principal evidence for the central role of Misrepairs in aging". arXiv:1505.01376 [q-bio.TO].
^ ^a ^b ^c ^d Goldsberry, Anne; Hanke, C. William; Hanke, K. W. (September 2016). "Sleep wrinkles: Facial aging and facial distortion during sleep". Aesthetic Surgery Journal. 36 (8): 931–940. doi:10.1093/asj/sjw074. PMID 27329660.
^ Poljsak, Boris (2016). "The Neglected Importance of Sleep on the Formation and Aggravation of Facial Wrinkles and Their Prevention". Journal of Cosmetics, Dermatological Sciences and Applications. 6 (2): 79–88. doi:10.4236/jcdsa.2016.62011 (inactive 21 January 2026).{{cite journal}}: CS1 maint: DOI inactive as of January 2026 (link)
^ "Everyone is Talking About: Silk Pillowcases". TRI Princeton. December 16, 2025. Retrieved 2026-01-20.
^ "Can Your Sleeping Habits Cause Wrinkles? Dermatologists Say Yes, and Share How To Prevent Them". Today. September 23, 2025. Retrieved 2026-01-20.
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^ "Best Silk Pillowcases of 2025: Tested and Reviewed". Good Housekeeping. 2025-11-20. Retrieved 2026-01-25.
^ TexTest (2025-12-29). "Independent laboratory test of multi-layer low-friction textile (ASTM D1894)". Zenodo. doi:10.5281/zenodo.18092440. Retrieved 2026-01-25.
^ Mark Changizi; Romann Weber; Ritesh Kotecha; Joseph Palazzo (2011). "Are Wet-Induced Wrinkled Fingers Primate Rain Treads?". Brain, Behavior and Evolution. 77 (4): 286–90. doi:10.1159/000328223. PMID 21701145.
^ Kareklas, Kyriacos; Nettle, Daniel; Smulders, Tom V (January 9, 2013). "Water-induced finger wrinkles improve handling of wet objects". Biol. Lett. 9 (2) 20120999. doi:10.1098/rsbl.2012.0999. PMC 3639753. PMID 23302867.
^ Haseleu, Julia; Omerbašić, Damir; Frenzel, Henning; Gross, Manfred; Lewin, Gary R. (2014). Goldreich, Daniel (ed.). "Water-Induced Finger Wrinkles Do Not Affect Touch Acuity or Dexterity in Handling Wet Objects". PLOS ONE. 9 (1) e84949. Bibcode:2014PLoSO...984949H. doi:10.1371/journal.pone.0084949. PMC 3885627. PMID 24416318.
^ Davis, N. (2021). "Water-immersion finger-wrinkling improves grip efficiency in handling wet objects". PLOS ONE. 16 (7) e0253185. Bibcode:2021PLoSO..1653185D. bioRxiv 10.1101/2020.11.07.372631. doi:10.1371/journal.pone.0253185.
^ "Dr Karl's Homework – Skin Wrinkles in Water (26/1/2000)". Abc.net.au. 2000-01-26. Retrieved 2019-04-30.
^ Einar P.V. Wilder-Smith; Adeline Chow (2003). "Water-immersion wrinkeling is due to vasoconstriction". Muscle & Nerve. 27 (3): 307–311. doi:10.1002/mus.10323. PMID 12635117. S2CID 45193684.
^ Einar P. V. Wilder-Smith (2004). "Water immersion wrinkling". Clinical Autonomic Research. 14 (2): 125–131. doi:10.1007/s10286-004-0172-4. PMID 15095056. S2CID 44938772.
^ H. Zhai, K.P. Whilem H. L. Maibach (2007). Dermatotoxicology. pp. 280–281.
^ G Alvarez, J Eurolo; P Canales (1980). "Finger wrinkling after immersion in water". British Medical Journal. 281 (6240): 586–587. doi:10.1136/bmj.281.6240.586-a. PMC 1713922. PMID 7427379.
^ The Dog Encyclopedia: The Definitive Visual Guide. Penguin. 15 August 2023. p. 84. ISBN 978-0-7440-8513-6.
^ ^a ^b ^c ^d Milosheska D, Roškar R (December 2022). "Use of Retinoids in Topical Antiaging Treatments: A Focused Review of Clinical Evidence for Conventional and Nanoformulations". Advances in Therapy. 39 (12): 5351–5375. doi:10.1007/s12325-022-02319-7. PMC 9618501. PMID 36220974.
^ ^a ^b Prabu K (28 August 2025). "A Review of Retinoid and Anti Aging Biochemistry". Journal of Biological and Molecular Sciences. 1 (1): 70–79. doi:10.64459/JBMS.2025.v1.i1.7. Retrieved 22 January 2026.
^ Brin MF, Lew MF, Adler CH, Comella CL, Factor SA, Jankovic J, O'Brien C, Murray JJ, Wallace JD, Willmer-Hulme A, Koller M (1999). "Safety and efficacy of NeuroBloc (botulinum toxin type B) in type A-resistant cervical dystonia". Neurology. 53 (7): 1431–8. doi:10.1212/WNL.53.7.1431. PMID 10534247.

TexTest (2025-12-29). "Independent laboratory test of multi-layer low-friction textile (ASTM D1894)". Zenodo. doi:10.5281/zenodo.18092440. Retrieved 2026-01-25. Third-party lab report showing average static COF 0.05 and kinetic COF 0.07 on multi-layer low-friction textile; redacted for confidentiality but verifiable core results.

External links

Skin Ageing at Medline