Four things you can see in a mirror: a hairline moving back at the temples, a thinning crown, a crease across the earlobe, and small yellow patches on the eyelids. In Copenhagen they were noted in 10,885 people, who were then followed for 35 years. Those with three or four of the signs went on to have 57% more heart attacks than those with none, after their age and the usual risk factors had been allowed for.
So the surface of the body carries information. That much is settled.
What is less settled is who can read it. In one test, three iridologists, who claim to see the state of the organs in the coloured part of the eye, were shown photographs of 143 people's eyes. Forty-eight of those people had kidneys failing badly enough to show in any blood test. The iridologists picked them out no better than chance.
Sherlock Holmes never ordered a blood test. He read tan lines, posture, calluses and ink stains. Conan Doyle borrowed the trick from Joseph Bell, his teacher at Edinburgh, who would bring a stranger into the lecture room and tell the class the person's trade, and where they had walked that morning, from the clay on their shoes.
Reading the body from the outside is medicine's oldest tool. About 2,400 years ago a Greek text set down the look of a person close to death: "the nose sharp, the eyes sunken, the temples fallen in". It is still called the Hippocratic face. Tongue, nails, skin and breath were all read as a matter of course before blood tests were routine. They arrived at the fringe by being left behind, and on the fringe they picked up company: maps, zones and systems that nobody had checked.
This article goes surface by surface, fourteen in all, and gives each a verdict on what it can tell you about your health: holds, partly holds, untested, or tested and failed.
The iris
Iridology holds that the iris is a map of the body, each zone tied to an organ, and that marks in a zone show trouble in the organ.
It began, the story goes, with an owl. Ignaz von Peczely, counted as its founding father, is said to have seen in a patient's eye the same streak he had seen as a boy in an owl whose leg he had broken. His own nephew later called the story apocryphal.
It has been tested more than any other method here. The kidney test opened this page. In a second test, five leading iridologists were shown the right eyes of 78 people, half of whom had an inflamed gallbladder full of stones, a condition iridology claims to spot easily. They were right 51% of the time, and they agreed with each other barely more often than chance allows. A review of the tests was published under the title "Iridology: not useful and potentially harmful".
There is a reason the result keeps coming back the same. The fine texture of the iris stays "remarkably stable over many decades", which is why it works as identification at border controls and on phones. Iridology needs the iris to change as health changes. A structure steady enough to be a passport cannot also be a diary.
Verdict. Tested and failed.
The back of the eye
The eye can be read. It takes the right instrument pointed at the right place.
Behind the iris, at the back of the eye, lie small blood vessels that a camera can photograph. Those photographs find the damage diabetes does "often before you notice any changes in your sight".
A machine has gone further. Trained on such photographs from 284,335 people, a program learned to estimate a person's age to within about three years, on average, and the upper blood pressure figure to within about 11 points, and to tell a man's eye from a woman's. None of that was thought to be written there.
There is information in the eye, then. It is at the back, where no iris-reader looks.
Verdict. Holds, with a camera.
The whites of the eyes
Two colours here mean something.
Yellow is jaundice. With darker urine and paler stools it points to the liver, and it is one of the few signs here that needs help the same day.
A blue tinge is the surprise. Among 169 hospital patients, three observers each graded the whites of the eyes. Blue-tinged whites were seen in 87% of those with iron-deficiency anaemia and in 5% of those with no anaemia. The sign every textbook teaches, a pale inner eyelid, was spotted in only one in five.
The wider claim, that each part of the white of the eye reports on a distant organ, has nothing of the kind behind it.
Verdict. Two colours hold. The maps do not.
The eyelids and the earlobe
Soft yellow patches on the eyelids, usually near the nose, are deposits of fat. Among 12,745 people in the same Copenhagen records, the one in twenty-three who had them went on to have 48% more heart attacks over the next 33 years. What stood out was that this held "independently" of the usual risks, cholesterol and other blood fats included.
A pale ring around the edge of the iris, common with age, was measured in the same people and predicted nothing by itself.
The earlobe crease is one of the four mirror signs from the opening. Nobody thinks the crease does the damage, any more than the hairline does. It is read as a mark of how fast the body is ageing, which the calendar does not show. The Copenhagen team's own last line was that "looking old for your age is a marker of poor cardiovascular health". Key Factors That Speed Up Aging (And How to Slow Them Down) has what happened when 1,826 twins were judged by their photographs.
Verdict. Holds, as a reason to have blood pressure, blood fats and blood sugar checked. A covers the first at home.
The tongue
What holds. A tongue that is sore, red and smooth goes with a shortage of B12 or folate, and a sore tongue is on the list for low iron. A red or white patch, or an ulcer, that is still there after three weeks needs looking at.
What partly holds. A scalloped edge, where the teeth leave a row of dents, has been put forward as a sign of sleep apnoea. Tested against overnight recordings in 61 people, it picked up about half of those who had apnoea and wrongly flagged a third of those who did not. A hint, then, and a weak one.
What is untested. The traditional Chinese map gives each region of the tongue to an organ: the tip, the sides, the root. It rests on centuries of practice. It has not been shown, in a controlled test, to find disease.
The coating is mostly a film of bacteria, and it is where most bad breath starts.
Verdict. Partly holds.
The nails
Spoon-shaped nails, grooves that date an illness, and clubbed fingertips are covered in 12 Signs Your Body Is Trying to Tell You Something Important. Three more belong here.
Terry's nails. The nail turns white, with a narrow darker band at the tip. They are found in 80% of people with severe liver disease, and also with heart failure, kidney failure and diabetes.
Half-and-half nails. White near the cuticle, red-brown over the far half, with a sharp line between. They turn up in 15% to 50% of people with long-standing kidney failure.
Muehrcke's lines. Paired white bands across the nail that vanish when you press on it and stay put as the nail grows, because they sit in the bed underneath. Described in 1956, they mark a steep fall in albumin, a blood protein.
Small pits across the surface go with psoriasis. White spots are knocks, as The Quiet Signals of Mineral Deficiency explains.
Much else is age. Nails grow thicker and more brittle with the years, and in the NHS's words nail problems "are not usually caused by anything serious".
Verdict. Holds. These are textbook signs, though most appear in people who already know they are ill.
The skin
Skin tags. Small soft growths in the folds of the neck and armpits. When 98 people with more than five of them were compared with 103 people without, the group with tags was several times as likely to show marked insulin resistance, after age, sex and waist had been allowed for. The test this points to is HbA1c, which gives average blood sugar over the past two to three months, and an does it by post.
Moles. A new mole, or an old one that changes size, shape or colour, may be melanoma, a skin cancer. Get it looked at. 12 Signs Your Body Is Trying to Tell You Something Important, linked above, has what to look for.
Face maps. The claim that spots on the forehead mean the gut and spots on the cheeks mean the lungs has no test behind it. The jawline in adult women is the one zone with a claim, as a clue that hormones are involved, and it is a loose one. When 374 adult women with acne were examined, nine in ten had it across several parts of the face. One in nine had it on the jaw alone.
Dark circles under the eyes are put down to "adrenal fatigue". A review that went through 58 sets of findings on that idea was published under the title "Adrenal fatigue does not exist".
The smell. A woman with an unusually sharp nose says she noticed her husband's scent change before he was diagnosed with Parkinson's. Chemists went looking for what she was smelling. They swabbed the oil from the upper backs of 64 people, 43 of them with Parkinson's, and found a distinct chemical signature in those who had it. She described its smell as "highly similar" to the one she knew. A folk observation, then, that survived being checked.
Verdict. Single signs hold, and so did one nose. The maps do not.
The urine
For centuries this was most of medicine. Until the 1500s, holding a flask of urine to the light was "the main standard of medical diagnosis". The chart that went with it showed twenty flasks in a ring, each a different colour tied to a disease. The practice was familiar enough to be mocked: a fourteenth-century window at York Minster shows monkeys doing it.
What survives of it is ordinary medicine.
Colour. Pale yellow is the target. Dark yellow and strong-smelling means drink more.
Pink, red or brown means blood until shown otherwise, and it needs checking even if it happens once and even if there is only a little. The exceptions are beetroot, which turns urine pink, and some medicines.
Froth that keeps coming back can mean protein is leaking through the kidneys.
The asparagus question. Among 6,909 people asked, 58% of the men and 62% of the women could not smell anything unusual in their urine after eating it. The difference tracked a stretch of DNA packed with smell-receptor genes. The claim "it does not do that to me" is mostly a statement about the nose.
Verdict. Holds.
The stool
No stained glass for this one. The readings are as plain as the urine's.
Black or dark red needs help the same day.
Blood that keeps appearing for three weeks needs checking. So does a stool that has been softer, thinner or longer than usual for three weeks.
The innocent causes. Iron tablets, liquorice and blueberries turn it dark. Beetroot, already excused once on this page, can make it look bloody, and so can tomatoes.
Pale, with yellow eyes and dark urine, belongs to the liver.
Verdict. Holds.
The breath
Most bad breath starts in the mouth. Three smells come from further in.
Fruity, like pear drops, is acetone. On a ketogenic diet it is expected and harmless. In someone who is thirsty, sick and not on such a diet, it is an emergency.
Like ammonia or urine goes with kidneys that have stopped clearing waste.
Sweet and musty is the smell of a failing liver. Its Latin name translates as "liver stench", and its nickname is "breath of the dead".
Both of the last two are late signs in people who are already seriously ill. Breath is read earlier than that in ordinary medicine: the standard check for H. pylori, a stomach bacterium that causes ulcers, is to swallow a tablet and breathe into a tube.
Verdict. Holds, mostly too late to be useful at home.
The pulse
Put two fingers on the inside of the wrist and count for one minute.
Rate. A normal resting pulse is usually between 60 and 100 beats a minute. Slower is generally better. Pooled across 46 sets of findings and 1.2 million people, every extra 10 beats a minute at rest went with 9% higher mortality.
Rhythm. The beats should come evenly. A pulse that is not steady is one of the main signs of atrial fibrillation, a common fault in the heart's rhythm that raises the risk of stroke and sometimes has no other symptom.
The watch. This reading has been handed to a machine. Among 419,297 people who wore a watch that checked their pulse, 2,161 were warned of an irregular rhythm. Heart monitors were posted to them and put on about two weeks later. Of the 450 that came back readable, a third showed atrial fibrillation, which fits a fault that can start and stop on its own. When the watch raised the flag again while the monitor was on, the monitor agreed 84% of the time.
The traditional reading. Chinese medicine reads the pulse at three positions and three depths on each wrist, each one assigned to an organ. Ayurveda has its own version, nadi pariksha. Neither has passed a controlled test of the kind the iris-readers failed.
Verdict. Rate and rhythm hold. The organ-reading is untested.
The hands
Grip. In 139,691 adults in 17 countries, the strength of a hand squeeze predicted death from any cause, and from heart disease, better than blood pressure did. The Harsh Truth About Aging: Decline or Longevity? has the figures and what to do about them. A is the cheap way to begin.
Colour. Fingers that turn white, then blue, then red in the cold are Raynaud's. It is usually harmless and occasionally a sign of something else.
A fine tremor, with a racing pulse, weight loss and a dislike of warm rooms, points to an overactive thyroid.
Verdict. Grip holds strongly. The rest are clues.
The ankles
Socks that leave a deep ring by evening, or a dent that stays when you press a thumb into the shin, mean fluid.
Usually it is a long day on your feet, a long sit, salty food or a medicine.
Both ankles, swollen for days, can come from the heart, the kidneys or the liver.
One leg, swelling suddenly for no reason you can name, needs help the same day.
Verdict. Holds.
The walk
How fast you walk without trying, and whether you can stand on one leg for ten seconds, both predict how long people live. The Harsh Truth About Aging, linked above, has both.
Posture is the oversold one. The claim that looking down at a phone wrecks the neck was tested in 150 adults aged 18 to 21. Neither their own account of their posture nor a trained assessor's rating of it had any link to neck pain.
Verdict. Pace and balance hold. Posture is less than it is sold as.
Reading them together
First, how to look. Use daylight and the same mirror, and take a photograph once a month: the tongue, the nails, the whites of the eyes. Changes over time are more informative than any single reading.
Then count. A single signal in isolation is less informative than two or three pointing in the same direction.
Yellow eyes or skin, dark urine, pale stools. The liver. Today.
Blue-tinged whites, a sore tongue, spoon-shaped nails. Iron. Ask for ferritin, the measure of the iron you hold in store.
Yellow eyelid patches, an earlobe crease, skin tags, a fast resting pulse. The heart and blood sugar. Blood pressure, blood fats and HbA1c. If they come back high, How to Fix Blood Sugar Spikes Naturally covers what low-carbohydrate eating does for them.
Frothy urine, half-and-half nails, both ankles swollen. The kidneys.
An unsteady pulse with breathlessness, chest pain or faintness. Now.
Six signs need no second one.
Lips, tongue or face turning blue or grey all at once. Now.
One side of the face drooping. Now.
Fruity breath with thirst and sickness, in someone who is not on a ketogenic diet. Now.
One leg that swells suddenly. Today.
A black or dark red stool. Today.
Pink, red or brown urine with no beetroot to blame. Get it checked, even if it happens once.
Each method earns its place or loses it on one question: does this observation go with a specific condition often enough to justify a test?
Holmes put the first step to Watson in one line: "You see, but you do not observe." Joseph Bell taught the whole method in three: observe carefully, deduce shrewdly, and confirm with evidence. The iris-readers managed the first two. The third is the one that sorts medicine from guessing.
The mirror from the opening costs nothing, and neither does a watch with a second hand.
Start with the pulse. One minute, tonight.
Noticed something new, and unsure what to do about it? How to Respond to a Symptom Without Ignoring It or Panicking — a calm way through a new symptom: what needs care today, what can wait, and what is worth watching.
Want to get better at noticing in the first place? Read Your Body's Signals: The Sense Most People Let Fade — the inward sense that reads hunger, tiredness and tension, and how to train it.
Know someone who has had their irises read? Send them this, and point them to the part about passports.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional. If you notice any of the warning signs described above, or a symptom is new, lasting or getting worse, get checked.
Affiliate Disclosure: This article contains affiliate links. As an Amazon Associate, All For Life earns from qualifying purchases, at no extra cost to you. We only link to products we would recommend without the commission.
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