What Has Not Been Measured: An Index of Evidence Gaps in Piercing
We did not set out to build this. It accumulated. Writing a guide to a piercing placement means reading the primary literature, and over eight placements the same thing kept happening: the figure everyone repeats turned out to have nothing behind it. After the fourth time it stopped being a curiosity and started being the finding.
So the entries below are not complaints about the research. They are a map of where a reader is being given a number that nobody produced. That seems worth having in one place, because the alternative is that each of these claims keeps circulating with a confident tone and no origin.
How to read an entry
Each entry records an absence, not a verdict. "We found no study" is a claim about the literature, not about the human body. It does not mean the effect is absent or that the convention is wrong. It means the measurement has not been published, so anyone stating the number is stating an opinion. We say where we searched so the claim can be checked and, where possible, overturned.
Two honest limits on all of it. Our searches ran through publisher sites, journal repositories and general search rather than a systematic database query, because PubMed returned a CAPTCHA and Europe PMC disallows automated access throughout this work. And where a primary source was paywalled or unreachable, the entry says so rather than guessing at its contents. Somebody with institutional access will find more than we did.
Anatomy nobody has measured
7 entriesEach of these is a dimension a piercer judges by eye and by hand, and which decides whether a piercing is possible or what length of bar it needs. In every case the measurement exists for some other purpose, or does not exist at all.
We found no study measuring tragus thickness. The published figure is vertical height, reported in one sample of 2,000 people as 15.44 ± 1.79 mm in men and 14.77 ± 1.54 mm in women. Height is not thickness, and thickness is the dimension that decides post length.
Where we looked: Piercing, dermatology, anatomy and plastic-surgery literature. Documented in: Tragus piercing
We found no study, in any discipline, measuring the depth or thickness of the fold above the navel — the single structure the entire trade says determines whether a navel can be pierced. Three measured umbilical datasets exist, all produced for abdominoplasty and umbilicoplasty, and all measure width, height and position on the torso.
Where we looked: Piercing, dermatology, anatomy and plastic surgery, including the three measured umbilical datasets. Documented in: Belly button piercing
We found no published measurement of the lateral nostril wall. The nasal soft tissue envelope has been measured in millimetres for rhinoplasty planning at the nasion, rhinion, supratip and tip, from 2.25 mm to 4.88 mm. The ala is not among the reported sites. One paper's methods section is paywalled and may contain an alar figure we could not read.
Where we looked: Rhinoplasty and facial-anatomy literature, restricted to academic domains. Documented in: Nose piercing
We found no published measurement of it. A 2016 study measured auricular cartilage thickness with callipers across 15 cadaveric specimens and dissected the superior and inferior crura as two separate sampling points — then reported the antihelix as a single region, without separating them. A 2024 review of auricular cartilage gives no millimetre values in its text and never mentions a crus of the antihelix.
Where we looked: Ear-reconstruction, otoplasty and tissue-engineering literature. Documented in: Rook piercing
We found no published measurement comparing conchal with helix cartilage thickness in a piercing context, and no source linking any thickness figure to a post length. The sentence that a conch needs a longer bar because the cartilage is thicker there is an explanation nobody has measured.
Where we looked: Ear anatomy and piercing literature. Documented in: Conch piercing
There is no published anatomical name for the pierceable membrane itself, no measurement of its dimensions, and no study of outcomes for correct versus incorrect placement.
Where we looked: ENT and anatomical literature. Documented in: Septum piercing
We found no source establishing that any proportion of ears lack a pierceable antihelix crus, and none quantifying how prominent the ridge is. The nearest published statement is that auricular cartilage folding varies between individuals, which is an observation rather than a measurement. Any percentage in circulation is unsourced.
Where we looked: Anatomical, surgical and clinical literature. Documented in: Rook piercing
Healing times nobody has established
5 entriesHealing figures are the most confidently stated numbers in this field and the least supported. Where we could trace a figure to a named source, we then looked for what stood behind it. In no case was that a cohort, a trial or a measurement.
Nobody has measured it. Every traceable figure is an uncited assertion and the published range runs from 3 months to 2 years. The two most-quoted figures are the same figure: a 2005 clinical review says up to 9 months, and an uncited consumer health page syndicated across several North American health systems repeats it word for word.
Where we looked: Clinical reviews, national health bodies, the professional association and named trade authorities. Documented in: Belly button piercing
We found no study of any design measuring it. Two institutional figures exist and disagree threefold — a Public Health England aftercare sheet says up to 6 months, a Californian health system says 2 to 4 months — and neither cites evidence. A 2005 clinical review's table of healing times omits the nose entirely, and a 2023 systematic review of 319 studies reports no nasal healing times.
Where we looked: Clinical reviews, systematic reviews, UK and US health bodies. Documented in: Nose piercing
The published spread is 3 months to 18 months and the two most-repeated figures contradict each other, neither carrying a citation. The NHS gives no figure and advises asking your piercer. A 2022 clinical review gives none either. One limit on our own claim: the trade body's 2013 procedure manual lists a healing-times section we could not reach across three attempts.
Where we looked: Clinical reviews, the NHS, the professional association's public guidance and manual. Documented in: Rook piercing
No health authority publishes a septum healing time at all. The figures that exist come from studios and retailers, are described as approximate, and cite no source.
Where we looked: Health authorities, professional bodies and published studio guidance. Documented in: Septum piercing
The six-to-twelve-month figure everyone repeats has no published source behind it, and the sources that would be expected to publish one decline to.
Where we looked: Health authorities, clinical reviews and professional bodies. Documented in: Helix piercing
Rates that do not exist
6 entriesThese are the numbers most often quoted with a percentage attached. We went looking for the numerator and the denominator.
We found no published rate of rejection or migration for navel piercings, or for any piercing site. There is no trial, no cohort and no registry. The 319-study systematic review has no rejection or migration category at all; the nationally representative survey does not break complications into types. The claim has no numerator and no denominator.
Where we looked: The three studies that would hold such a figure if it existed. Documented in: Belly button piercing
We found no navel-specific hospital admission rate anywhere. The only nationally representative survey reports admission for all 754 piercings in 16 to 24 year olds combined, at 0.9%, with no breakdown by site. Any site-specific figure is an extrapolation.
Where we looked: The published survey PDF, re-read to confirm the table has no site breakdown. Documented in: Belly button piercing
We found no study of any design that separates rook outcomes from other upper-ear cartilage. The word rook appears in none of the major piercing-complication reviews; the largest uses a single category for the whole ear.
Where we looked: The two largest pooled complication sources and the transcartilaginous infection literature. Documented in: Rook piercing
What nobody has published is a comparison between the helix and the earlobe. The claim has no study behind it, in either direction.
Where we looked: Dermatology and piercing literature. Documented in: Helix piercing
We found no published case of jewellery embedding in the conch, and none of migration or rejection of conch jewellery.
Where we looked: Case reports, case series and the pooled complication literature. Documented in: Conch piercing
We found no incidence figure for granuloma or keloid at the rook, or at any upper-ear sub-site.
Where we looked: Dermatology and ear-piercing complication literature. Documented in: Rook piercing
Jewellery choices with no evidence behind them
6 entriesEvery size chart in this industry, including ours, describes convention. We went looking for the study that set the convention.
We found no study, at any level of evidence, testing whether any jewellery parameter changes rejection, migration or complication rates — at the navel or at any site. The mechanism is asserted in a clinical review and by the professional association, both without data.
Where we looked: Trials, cohorts, retrospective series and registries; and the three pooled sources checked directly. Documented in: Belly button piercing
We found no source at any level of evidence publishing a fresh-versus-healed bar length, for the navel or any other site. The professional association says only that many piercings require a downsize before healing is complete, naming no site, no length and no timeframe.
Where we looked: Professional-association guidance, regulators' guidance and clinical reviews. Documented in: Belly button piercing
We found no study comparing jewellery geometry at any ear cartilage site. The reason usually given — that a lower curvature puts less strain on a healing channel — traces to uncited text. The professional association's guidance on jewellery for initial piercings does not mention the rook, does not mention curved barbells by name, and gives no gauge number for any site.
Where we looked: Comparative studies at any ear cartilage site; professional-association guidance read in full. Documented in: Rook piercing
We found no published evidence comparing hoops with flat back studs during healing, and the trade body does not state the rule in those terms.
Where we looked: Comparative studies and trade-body guidance. Documented in: Helix piercing
We found no comparative study on jewellery material and healing outcome. Nobody should tell you titanium heals faster — including us. What the evidence supports is that implant-grade titanium to ASTM F136 contains no nickel by specification, which is a different claim.
Where we looked: Comparative studies on material and healing outcome. Documented in: Helix piercing
We found no published evidence that downsizing improves healing outcomes or reduces bumps, and none on initial jewellery length and swelling.
Where we looked: Published evidence on initial jewellery length, swelling and bump formation. Documented in: Helix piercing
Aftercare and daily life, untested
6 entriesThis is the advice given most often and with the most confidence. It is also where two UK regulators and the American trade body disagree with each other, none of them citing evidence.
We found no comparative evidence that any aftercare method changes outcomes, at the navel or at any other site. No randomised trial, no comparative cohort. Sterile saline against soap against leaving it alone is, on the published record, untested — while the guidance itself conflicts between two UK local authorities and the US trade body.
Where we looked: Trials and comparative cohorts; and the guidance documents themselves, read directly. Documented in: Belly button piercing
We found no trial or comparative study of any aftercare regimen at a nostril piercing. The one nose-specific instruction from a named public-health publisher — that antibacterial wash is not suitable for nostrils, septum or vertical lips — cites no evidence for it.
Where we looked: Trials and comparative studies; UK and US public-health guidance. Documented in: Nose piercing
We found no published evidence that side-sleeping delays cartilage healing or causes bumps, and nothing at all published on pressure, pillow contact or mechanical irritation at upper-ear cartilage piercings. Oddly, sustained pressure is a dermatological treatment for keloids, which nobody has reconciled with the pillow claim.
Where we looked: Clinical, anatomical and dermatological literature. Documented in: Helix piercing
We found no published evidence that external pressure from over-ear headphones, glasses, helmets or sleeping delays healing of a cartilage piercing.
Where we looked: Clinical and dermatological literature. Documented in: Conch piercing
We found no indexed evidence that it does anything for piercing bumps, keloids or hypertrophic scars.
Where we looked: Indexed dermatology literature. Documented in: Helix piercing
We found no published evidence either way on piercing several cartilage holes in one session.
Where we looked: Published evidence on multiple simultaneous cartilage piercings. Documented in: Helix piercing
Claims about effects on the body, untested
6 entriesThese are the claims that bring most people to the subject. They are also the ones where the gap between what is said and what has been measured is widest.
We found no published study of any kind — randomised, observational, case series or single case — testing whether static jewellery worn in the tragus produces any physiological effect. Not on heart rate, heart-rate variability, appetite, migraine, tinnitus or anxiety. Separately, whether the tragus carries auricular vagus fibres at all is unresolved in the anatomical literature.
Where we looked: Four documented search strategies: the clinical databases, the stimulation protocol and review literature, the clinical case literature on tragus piercing, and the patent literature. Documented in: Tragus piercing
There has never been a controlled trial of daith piercing for migraine. We found no statement on daith piercings from the NHS, the Mayo Clinic or the Migraine Trust.
Where we looked: Controlled trials; national health bodies and migraine charities. Documented in: Daith piercing
No. The authors of the only peer-reviewed paper naming the rook in a headache context state that the literature is insufficient to judge whether the piercing's location affects migraine symptoms. The entire argument rests on a distinction nobody has tested.
Where we looked: The headache and auricular-stimulation literature. Documented in: Rook piercing
Almost nobody has looked. The nose is the main human reservoir of S. aureus, and on the interaction with piercing the whole published record is one 2013 conference poster abstract — which reports an association without publishing a percentage, an odds ratio or a piercing-specific p-value — and one assertion in a 2020 case report whose only citation is a paywalled one-page history piece. We found no peer-reviewed study measuring carriage in pierced against unpierced noses, and no study culturing nose jewellery.
Where we looked: Clinical databases, the carriage literature, and the piercing case literature. Documented in: Nose piercing
We found no study testing whether a piercing affects appetite, hunger, food intake or body weight, by any method. The patent usually cited for the claim describes a clip with pressure projections rather than a piercing, and its claims never mention appetite, hunger or weight.
Where we looked: Clinical databases and the patent literature, with the patent claims read in full. Documented in: Tragus piercing
The usual explanations — a pressure point, an acupuncture point, the sneeze reflex — have no source behind them, and nobody has published on tearing during a septum piercing specifically.
Where we looked: Ophthalmic and ENT literature. Documented in: Septum piercing
Things the field has not agreed on
6 entriesNot every gap is a missing measurement. Some are definitions and rules that different authorities state differently, with nothing to arbitrate between them.
Nobody has measured it. Every numbered pain scale in circulation traces back to studio blogs and retailer pages with no stated method, no sample and no source — including pages that sell the jewellery.
Where we looked: Pain-measurement literature and the sources behind the published scales. Documented in: Septum piercing
We found four mutually incompatible definitions, and no definition of conch orbital in any peer-reviewed, government, licensing or professional-body source. The real anatomical division is the cymba and the cavum conchae, and no source we read maps the popular terms onto it.
Where we looked: Peer-reviewed, government, licensing and professional-body sources. Documented in: Conch piercing
The sources disagree and none reconciles them. The only peer-reviewed paper describing a rook anatomically places it at the inferior crus of the antihelix; piercing sources almost always say superior crus. Those are two different named structures.
Where we looked: Clinical, anatomical and trade sources. Documented in: Rook piercing
No source we read gives a definition that distinguishes them operationally. The reviews treat migration and rejection as a continuum without defining a threshold.
Where we looked: Clinical reviews and professional-association guidance. Documented in: Belly button piercing
We found no clinical study, no case series and no case report comparing dermal punching with needling in ear cartilage, and none on complications of punching at any site. The comparison every argument about punching assumes has never been published, in either direction. We also found no English local-authority byelaw or guidance that explicitly permits or prohibits it.
Where we looked: Clinical literature; English local-authority byelaws and guidance. Documented in: Conch piercing
In the two jurisdictions we checked, no. The word cartilage does not appear anywhere in the English Department of Health guidance on regulating cosmetic piercing, which also states there is no statutory age of consent for cosmetic piercing. California's statute excludes the piercing of an ear from its definition of body piercing without qualifying which part.
Where we looked: UK statute and departmental guidance; one US state statute. We checked one state, not fifty. Documented in: Rook piercing
What this page is not
It is not a claim that piercing is unstudied. The clinical literature on piercing complications is real and in places excellent: there is a nationally representative English survey of 10,503 adults, a systematic review pooling 319 studies, a systematic review of transcartilaginous infections, and a 2025 UK outbreak investigation that traced ten cases to one studio’s water system. Where that evidence exists we cite it and follow it.
It is also not a sales argument. Several entries count against our own copy. We sell jewellery in sizes whose conventions have no study behind them, and the index says so. We would rather state that than let a size chart imply a precision nobody has earned.
And it is not finished. Each new guide adds entries, and we expect some to be removed when somebody points us at the study we missed.
If you know of a study that closes one of these gaps, email belorajewelryuk@gmail.com with the citation. We will read it, correct the entry, and log the change on this page with the date — the same commitment we made on our materials index and have honoured there.
This index is published under a Creative Commons Attribution 4.0 licence. Researchers, journalists, piercers and competing retailers may quote or reproduce it with attribution to Belora Jewelry and a link to this page. We would rather it travelled than stayed ours.
Corrections log: none yet.
Every entry on this page traces to a sourced guide published by Belora Jewelry, and the searches behind each absence were run between 22 and 26 October 2026. Belora sells jewellery and does not provide medical or legal advice. Nothing here is a treatment recommendation or a statement of what is lawful where you live. An absence of published evidence is not evidence of absence, and nothing on this page should be read as a reason to disregard your piercer or a clinician. If a piercing is hot, swollen, spreading, producing coloured pus, or if you feel unwell, seek medical help promptly.