Why Do Your Fingers Get Wrinkly in Water?

The child listens. The parent reads. This page helps you answer the questions your child may ask after the story. You can see the story script with the script button while it plays.

What this story is about

After a bath or a swim, the tips of the fingers and toes get wrinkly. The wrinkles form on skin with no hair: the fingers, the palms, and the soles of the feet (PMID 24416318). The story is less about the answer itself and more about how people found it out. It starts with one observation. When the nerve to a finger is cut, only that finger stays smooth in water. From there, it goes to the finding that the wrinkles come from narrowing blood vessels, and the nerve controls this. It ends with a question that is still open: why do we have this at all? The tests of that question do not agree yet.

The answer people often hear: "the skin soaked up water"

This is the answer a child has most likely heard. In everyday belief, people often explain the wrinkles as a local osmotic effect in the skin, meaning water moving into the skin (DOI: 10.1159/000328223). It is true that water goes into the skin. In one study that measured how much water skin takes up, hairy skin took up much more water than skin with no hair (PMID 9730110). The wrinkles, however, form on the skin with no hair (PMID 24416318). That water study did not measure wrinkles, so we do not join these two facts into a conclusion.

The evidence that this answer is not enough came from nerves. When the nerve to a finger is cut, that finger does not wrinkle (DOI: 10.1159/000328223). A 2006 study of reattached fingers asked a direct question. Are the wrinkles caused by the sympathetic nerves, or by something in the skin itself? The reattached fingers, which had lost their nerve supply, did not wrinkle. The authors took this as a sign that the nerve supply is important (PMID 16612557). There is also a measurement that compares wrinkles with swelling. In 39 healthy adults, how much the whole hand swelled after soaking (hand volume) was not related to how much it wrinkled (PMID 35348207). But this measured the volume of the whole hand. It did not directly measure how much water the outer skin took up. Water still has a part to play. It probably enters the skin through the sweat ducts and is the starting point that sets off the nerves (PMID 15095056).

How people found out

The finger with a cut nerve. It began with what surgeons saw. A 2011 paper says that "nearly a century ago" surgeons observed that no wrinkles form when the nerve to a finger has been cut (DOI: 10.1159/000328223). The name of the first person and the exact year are not in the abstracts we collected. Comparing an injured finger with the healthy finger on the other hand is still how later studies work (PMID 35614228). In a 1977 study, all 24 patients with a recent, complete nerve injury had no wrinkles on the skin served by the injured nerve (PMID 907018). But 8 patients whose nerves were squeezed, not cut, still wrinkled, even when their feeling was weaker (PMID 907018). No wrinkles is a sign of nerve injury, but wrinkles do not prove the nerve is healthy. A 1979 paper said that the wrinkles depend on working sympathetic nerves. Damage to the sympathetic pathway, either in the brain and spinal cord or out in the limb, takes the wrinkles away (PMID 420620). The sympathetic nerves are the nerves that control body jobs like blood vessels and sweat glands, without our thinking about them.

It becomes a test. A 1973 paper described a simple test. You put the hand in warm water to see if the sensory nerves of the hand are connected, or growing back. The test results matched what was found during operations (DOI: 10.1136/bmj.3.5881.615). A 2015 review says that wrinkling in water has been used to check limb nerves for more than 80 years (PMID 25216595). The test is most useful for patients who cannot answer well. Hand nerves are usually checked by asking if the person can tell two touching points apart. This is hard for patients who are unconscious, very young, or unable to work with the doctor. Putting the fingertip in water and watching for wrinkles is a pain-free choice (PMID 17057149). This method comes from a single case report (PMID 17057149). In a finger whose nerve has grown back or been repaired, the wrinkles come back at least partly (PMID 15862367).

One study looked at 70 patients (85 nerves) who might have finger nerve injuries, and checked against what surgery found. The wrinkle test had a sensitivity of 69.5% and a specificity of 62.5%. When it was positive together with the two-point test, the chance of a nerve injury was 92% (PMID 31688116). So the wrinkle test alone can miss an injury, or point to one that is not there, quite often. Another study looked at 20 people who had surgery to repair a finger nerve. A positive result took 24.5 minutes on average, and 1 in 4 needed 40 minutes (PMID 35614228). The authors wrote that with the usual 30-minute limit, up to 25% of tests may be false negatives (PMID 35614228). Beyond hand injuries, the test is also being studied as a helper test for the function of very thin nerve fibers (PMID 18270233, PMID 42595323).

The blood vessels get narrow. Scientists found what the nerve does by measuring blood flow. A 2003 study measured how fast blood moved in the arteries and the finger skin of healthy people. They measured before and during wrinkling. During wrinkling, blood flow speed dropped clearly in all the vessels, and it dropped the most in the finger vessels (PMID 12635117). The authors concluded that wrinkling in water comes from vasoconstriction in the fingertip (PMID 12635117). Vasoconstriction is when the blood vessels, the tubes that carry blood, get narrow.

The same team then made the vessels narrow with no water. They put a cream that narrows blood vessels (EMLA, a numbing cream) on the fingertips. In 25 healthy volunteers, the wrinkle scores and the drop in finger blood flow were almost the same as after soaking in water (PMID 12826076). A plain water-based cream was used as a control. With it, there were very few wrinkles, and the drop in finger artery blood flow was not significant (PMID 12826076). What this shows is that even without soaking in water, narrowing the blood vessels makes almost the same wrinkles.

There is also a check from the other side. One study used 20 fingers that had been cut off and reattached, on average 17.5 months before. The fingers were soaked in warm salt water. In normal fingers, blood flow fell by 27.6% and the skin wrinkled. In the reattached fingers, blood flow rose by 22.8% and the skin did not wrinkle (PMID 16612557). In 14 reattached fingers, the EMLA cream also only widened the vessels and made no wrinkles (PMID 17707406). The authors read this to mean that even the cream needs working sympathetic nerves to narrow the vessels (PMID 17707406).

Why narrow vessels make wrinkles. Here is the proposed explanation. When the vessels narrow, the fingertip loses volume. This creates a pulling force inside the fingertip, which pulls the skin on top down into wrinkles (PMID 15095056, PMID 25216595). The 2015 review calls this "postulated" (PMID 25216595), and the 2004 review proposes the same mechanism (PMID 15095056). One finding fits this idea. An ultrasound study found small fluid-filled pockets between tissue layers inside the tips of the fingers and toes. After wrinkling, these spaces were half their earlier size, and the authors thought these spaces take part in wrinkling (PMID 30733554).

What water does. The part water plays is not fully worked out. A 2004 review suggests ("probably") that water goes into the skin through the sweat ducts. There it changes the salt balance of the outer skin, which sets off the nearby nerves and leads to vasoconstriction (PMID 15095056). A 2025 study in 24 healthy adults changed the liquid. In soybean oil, ice water, an alkaline liquid, and very salty water, no wrinkles came even after 30 minutes. The same was true with a cuff on the arm that reduced blood flow (PMID 40451152). Warm water, distilled water, and higher water pressure made wrinkles come faster (PMID 40451152). Another study (14 people, 28 hands) found that the saltier the liquid, the slower the wrinkles came. That study says the exact way it works is still argued about (PMID 15862367).

Questions your child might ask

"Is it bad for me when my fingers get wrinkly?" No. Wrinkling of the palms in water is normal and goes away (PMID 42595323). You can tell your child the skin gets smooth again some time after leaving the water.

"Is it the same as the wrinkles on Grandma's face?" They are different. In a study of 39 healthy adults, wrinkling in water was not related to face wrinkles. It was also not related to how much the hand swelled after soaking (PMID 35348207). In the same study, older people had lower wrinkle scores. Sex, body mass index, and physical activity were not related (PMID 35348207). The studies we collected did not compare children.

"Why doesn't the back of my hand get wrinkly?" The wrinkles form on skin with no hair: the fingers, palms, and soles (PMID 24416318). One explanation is that palm skin has many special blood vessels that are closely linked to sympathetic nerves. This comes from one researcher's hypothesis paper (PMID 24080203). Water is thought to enter through the many sweat ducts of the palms and soles (PMID 15095056). But one study measured that hairy skin takes up more water (PMID 9730110). So it is better not to say "the back of the hand drinks less water."

"How long does it take?" It is very different from person to person. One study put the fingers of 24 healthy adults in room-temperature water. The time to clear wrinkles (grade 3) ranged from 2.1 to 37.0 minutes (PMID 40451152). In the same study, 10 a.m. was faster than 10 p.m. (average 10.4 vs. 14.6 minutes) (PMID 40451152). This is one study of 24 adults, so for a child, "people are very different" is enough.

What is known, and what is still open

What is known. The wrinkles need a nerve. A finger with a fully cut nerve does not wrinkle (PMID 907018, PMID 16612557). Because of this, wrinkling has been used as a nerve test for decades (PMID 25216595). During wrinkling, blood flow in the finger vessels drops (PMID 12635117), and narrowing the vessels without water makes almost the same wrinkles (PMID 12826076).

Still open, part 1: how. How narrow vessels fold the skin (loss of volume and a pulling force) is a proposed explanation (PMID 15095056, PMID 25216595). How water first sets off the nerves is also still a guess (PMID 15095056).

Still open, part 2: why. The idea that the wrinkles are there to help us hold wet things has mixed test results.

• A 2011 paper says it gives evidence that the wrinkles are not an accident of being wet, but were selected to improve grip in wet conditions. It reported that the shape of the wrinkles has the signature features of drainage networks, which carry water away (DOI: 10.1159/000328223). The title compares them to "rain treads," the grooves in car tires. This paper's evidence is a study of the wrinkle shape.
• In a 2013 test, wrinkly fingers handled objects under water more quickly, and there was no difference with dry objects (PMID 23302867). The authors wrote that this supports the idea, and that the wrinkles "may" be an adaptation for handling objects in wet conditions (PMID 23302867). The abstract does not give the number of people.
• A 2014 test gave 40 people a hand skill task, and also used two touch tasks. Wrinkles did not improve skill with wet objects, and did not change any kind of touch that was measured (PMID 24416318). The authors concluded that the wrinkles seem to have no significant effect on skill with wet or dry objects (PMID 24416318).
• A 2021 test measured how people matched their grip force to the load on an object. It compared dry fingers, wrinkly fingers, and wet fingers that were not wrinkly. Wrinkly fingers lowered the grip force needed for a wet object, to about the level needed for a dry object (PMID 34288934). The authors wrote that better grip in watery places is a "possible" adaptive reason for the wrinkles (PMID 34288934). The abstract does not give the number of people.

The four studies measured different things: shape, speed of handling, skill score, and grip force. So it is hard to say that one study directly overturns or confirms another. A 2025 study on wrinkle shape describes wrinkling in its introduction as "an evolutionary mechanism that increases grip strength in water" (PMID 39965356). But what it actually measured was whether the wrinkle pattern comes back in the same places over time (PMID 39965356).

Things to try together

• Within your usual bath time, time together how long it takes until the wrinkles are clear (grade 3 in the study). Do not make the bath longer. If no wrinkles come, "none" is a result, too. The study's numbers are for adults in room-temperature water, so a warm bath is a different condition. Comparing family members links to the finding that people are very different (PMID 40451152).
• Compare the fingertips, the toes, and the back of the hand. Let your child say which ones wrinkle and which stay the same.
• Try moving small toys in water with wrinkly fingers and with smooth fingers. Tell your child first that the studies disagree, and then ask, "Which did you get?" This shows why trying a test again matters.
• The normal range is wide, so late or few wrinkles are fine. In healthy adults, the time ranged from 2.1 to 37.0 minutes (PMID 40451152), and older people had fewer wrinkles (PMID 35348207). One report also found clearly fewer wrinkles in people who work with their hands (PMID 6734390). Please do not judge nerve health from a home test. If a hand feels strange after an injury, that is for a doctor to check.
• For safety: do not make the bath longer to see wrinkles, and young children should do this only with an adult nearby. Do not make the water hot to get wrinkles faster. Use your usual bath temperature. Some studies used ice water, very salty water, a cuff squeezing the arm to reduce blood flow, EMLA cream (a numbing medicine), vinegar, and caffeine. None of these are for home experiments.

Sources

• "Are Wet-Induced Wrinkled Fingers Primate Rain Treads?" (2011) — DOI: 10.1159/000328223 — Notes the century-old observation that fingers with a cut nerve do not wrinkle, and argues that wrinkles have the shape of drainage networks, selected for grip in wet conditions.
• "Comparison of the finger wrinkling test results to established sensory tests in peripheral nerve injury." (1977) — PMID 907018 — All 24 patients with a recent complete nerve injury had no wrinkles in that area; 8 with nerve compression still wrinkled.
• "Skin wrinkling on immersion of hands: a test of sympathetic function." (1979) — PMID 420620 — Wrinkling depends on intact sympathetic nerves and is a simple, reliable test.
• "New and Simple Test of Nerve Function in Hand" (1973) — DOI: 10.1136/bmj.3.5881.615 — Describes a warm-water test of sensory nerve supply and regrowth in the hand; results matched surgical findings.
• "Stimulated skin wrinkling as an indicator of limb sympathetic function." (2015) — PMID 25216595 — Used for more than 80 years; wrinkling depends on finger vasoconstriction, and a volume-loss mechanism is postulated.
• "Case of the month: The skin wrinkle test: a simple nerve injury test for paediatric and uncooperative patients." (2006) — PMID 17057149 — A pain-free way to check finger nerves in young or uncooperative patients.
• "Fingertip skin wrinkling - the effect of varying tonicity." (2005) — PMID 15862367 — Saltier liquids slowed wrinkling; the exact mechanism is still debated.
• "The Utility of Diagnostic Tests for Digital Nerve Injury." (2020) — PMID 31688116 — Wrinkle test sensitivity 69.5%, specificity 62.5%; 92% predictive probability together with the two-point test.
• "The optimal duration for the wrinkle test in a clinical setting." (2022) — PMID 35614228 — In 20 nerve-repair patients, a positive result took 24.5 minutes on average; a 30-minute limit may give up to 25% false negatives.
• "Skin wrinkling for diagnosing small fibre neuropathy: comparison with epidermal nerve density and sympathetic skin response." (2008) — PMID 18270233 — Wrinkling is a useful helper test when other tests are not available.
• "The skin-wrinkling test: principles and clinical applications." (2026) — PMID 42595323 — Palm wrinkling is normal and reversible; the test is quick and cheap.
• "Water-immersion wrinkling is due to vasoconstriction." (2003) — PMID 12635117 — Blood flow speed fell most in the finger vessels during wrinkling; wrinkling comes from fingertip vasoconstriction.
• "Water immersion and EMLA cause similar digit skin wrinkling and vasoconstriction." (2003) — PMID 12826076 — In 25 people, a vessel-narrowing cream caused almost the same wrinkles and blood flow drop as water; a control cream did not.
• "Paradoxical response to water immersion in replanted fingers." (2006) — PMID 16612557 — 20 reattached fingers had more blood flow and no wrinkles, suggesting sympathetic nerves are important.
• "EMLA and water immersion cause similar vasodilatation in replanted fingers." (2007) — PMID 17707406 — In reattached fingers, both cream and water widened vessels and made no wrinkles.
• "Water immersion wrinkling--physiology and use as an indicator of sympathetic function." (2004) — PMID 15095056 — Proposes that water enters through sweat ducts, sets off nerves, and vasoconstriction with a pulling force wrinkles the skin.
• "Fluid Containing Structures in the tips of the fingers and toes delineated by Ultrasound Imaging before and after Induced Skin Wrinkling." (2019) — PMID 30733554 — Fluid spaces in the fingertip were half their size after wrinkling.
• "Influence of Physical, Chemical, and Sympathetic Stimuli on Water-Immersion Finger Wrinkling." (2025) — PMID 40451152 — In 24 adults, time to wrinkling ranged from 2.1 to 37.0 minutes; oil, ice water, and very salty water gave no wrinkles in 30 minutes.
• "Effects of hydration on tactile sensation." (1998) — PMID 9730110 — Hairy skin took up much more water than skin with no hair (wrinkles were not measured).
• "Decreased skin wrinkling in diabetes mellitus." (1984) — PMID 6734390 — Wrinkling was clearly lower in people with diabetes and in manual workers; the cause was not explained.
• "Water immersion skin wrinkling: modulation by common participant characteristics." (2022) — PMID 35348207 — In 39 adults, wrinkling was lower with older age and was not related to face wrinkles or hand swelling.
• "Aquagenic wrinkling of the palms is due to vasoconstriction of palmar skin vasculature." (2013) — PMID 24080203 — Hypothesis that palm skin lets water in easily and has many blood vessels closely linked to sympathetic nerves.
• "Water-induced finger wrinkles improve handling of wet objects." (2013) — PMID 23302867 — Wrinkly fingers handled objects under water faster; no difference with dry objects.
• "Water-induced finger wrinkles do not affect touch acuity or dexterity in handling wet objects." (2014) — PMID 24416318 — In 40 people, wrinkles changed neither skill with wet objects nor touch.
• "Water-immersion finger-wrinkling improves grip efficiency in handling wet objects." (2021) — PMID 34288934 — Wrinkly fingers lowered grip force for wet objects to the level used for dry objects.
• "On the repeatability of wrinkling topography patterns in the fingers of water immersed human skin." (2025) — PMID 39965356 — The direction of wrinkle patterns repeated at two time points.