Salt in the history of medicine

We shall take a journey through the history of the use of salt in medicine and discover that empirical knowledge of the benefits - and sometimes drawbacks of salt - has been a hallmark of many civilizations.
 
"There must be something sacred in salt. It is in our tears and in the ocean." (Khalil Gibran)

When Lot's wife looked back to catch a last glimpse at the burning city of Sodom, she turned into a pillar of salt. Roman priests scattered salt where the city of Carthage once stood to prevent any return of life. These allegories contradict what we know about salt today. Dissolved common salt (sodium chloride) is present in all the human body and plays crucial physiological roles in life-sustaining processes (a). Life cannot exist without salt. But when did salt become associated with healing powers? And what are its healing powers? (1) (2) (3) (4) (5) 

Our journey through the history of medicine will illustrate how the properties of salt have been viewed with time.
 

Salt in Egyptian medicine

Salt is mentioned as an essential ingredient in medical science in some of the oldest medical scripts. The ancient Egyptian papyrus Smith, which is thought to refer to the famous master-builder and doctor Imhotep of the third pre-Christian millennium, recommends salt for the treatment of an infected chest wound. The belief was that salt would dry out and disinfect the wound (b). The papyrus Ebers (1600 B.C.) describes many salt recipes especially for making laxatives and anti-infectives. They were dispensed in either liquid, suppository or ointment form. For instance, there was a suppository containing honey, vegetable seeds and ocean salt that was used as a laxative and one with incense, vegetable seeds, fat, oil and ocean salt against anal infections. Salt-based remedies were also prescribed for callous skin, epidemic diseases, to check bleeding, as an eye ointment, and to accelerate childbirth (a vaginal suppository).
 

Salt in Greek medicine

Both sea salt and rock salt were well known to the ancient Greeks who noted that eating salty food affected basic body functions such as digestion and excretion (urine and stools). This led to salt being used medically. The healing methods of Hippocrates (460 BC) especially made frequent use of salt. Salt-based remedies were thought to have expectorant powers. A mixture of water, salt, and vinegar was employed as an emetic. Drinking a mixture of two-thirds cow's milk and one-third salt-water, in the mornings, on an empty stomach was recommended as a cure for diseases of the spleen. A mixture of salt and honey was applied topically to clean bad ulcers and salt-water was used externally against skin diseases and freckles. Hippocrates also mentions inhalation of steam from salt-water. We know today that the antiinflammatory effects of inhaled salt provide relief from respiratory symptoms (c). Thus, 2000 years ago, Greek medicine had already discovered topical use of salt for skin lesions, drinking salty or mineralized waters for digestive troubles and inhaling salt for respiratory diseases!
 

Roman salt-containing recipes

The Roman military doctor Dioskurides (100 A. D) is regarded as one of the most important medical authors of Antiquity. His work Materia Medica summarises the botanical and pharmacological know-how of his time. Dioskurides considered "honey-rain-ocean water" to be an excellent emetic. Salty vinegar was helpful against "binging and rotting callosities" and bites (dogs and poisonous animals), to check bleeding after surgery, as a gargle to kill leeches and to get rid of "scab and crust". Salt added to wine and water was a laxative. 

Both sea and rock salt were used in remedies but rock salt was considered to be the strongest. The salt was generally mixed with other ingredients (e.g. vinegar, honey, fat, flour, pitch, resin) and could be dispensed in several forms (drink, suppository, clyster (enema), ointment, oil). The main recommended indications were skin diseases, dropsy, infections, callosities, ear-ache, mycosis, digestive upsets, sciatica.
 

The inheritance of classical Antiquity

The Greek doctor Galen from Pergamon (129–200 A.D.), physician-in-ordinary to the Roman emperor Marcus Aurelius, summarised the medical concepts of antiquity and left his mark on western medicine for over 1000 years. His medical system also made use of salt (sea salt, rock salt, salt foam) in recipes against many diseases: infectious wounds, skin diseases, callosities, digestive troubles. His list of salt-containing remedies also included emetics and laxatives.
 

Salt in the Arab world

Eight hundred years later, the medical precepts of the well-known Arab doctor and scientist Avicenna (Ibn Sina, 980–1037 A.D.) laid the foundations of modern scientific medicine. His recipes also used salt. He emphasised the presence of iodine and iron in coastal sea salt. The Jewish doctor Maimonides (1135–1204 A.D.), physician-in-ordinary to the caliph in Persia, wrote in hisDianetic for soul and body that only bread with enough salt was healthy food.
 

Salt in medicines of the Middle Ages

The School of Salerno (11th -13th Century A.D.) founded western European academic medicine in the Middle Ages. It is seen as the first European university to bring together medical knowledge of Greek and Arab origin and transcribe it in latin. Its writings reveal an awareness of the use of a mixture of salt, oil and vinegar as an emetic and of suppositories of salt and honey as an effective remedy against constipation (see Egyptian medicine above). Powdered and roasted salt was said to have a pain-killing effect and rock salt was considered to be a good remedy against fever. 

The School published a book on The Art of Staying Healthy which was a collection of sayings and poems providing Crusaders with life regimens they could understand. It was in fact one of the first popular medical manuals for people versed in latin and for academically trained physicians. The book explicitly recommended salted bread and food. Salt not only made food tasty but drove off toxins. However, it also warned against too much salt: "Too salty food diminishes semen and eyesight – salt burns, makes one fretful, shabby, scabby and wrinkly."
 

Salt in Renaissance medicine

The doctor and alchemist Paracelsus (1493–1541 A.D.) introduced an entirely new medical concept. He believed that external factors create disease and conceived a chemically oriented medical system which contrasted with the prevalent herbal medicine. Only salted food could be digested properly: "The human being must have salt, he cannot be without salt. Where there is no salt, nothing will remain, but everything will tend to rot." He recommended salt water for the treatment of wounds and for use against intestinal worms. A hip-bath in salt water was a superb remedy for skin diseases and itching: "This brine - he said - is better than all the health spas arising out of nature." He described the diuretic effect of salt consumption and prescribed salt preparations of different strengths that were used for instance against constipation.
 

Salt in 16th-19th century pharmacies

The pharmacies of the 16th century continued to relate the various uses of salt to its external aspect (rock salt, sea salt, refined salt and roasted salt). Respect for salt was as deep as prices were high. Until the 18th century, the preferred and most common pharmacy salt was rock salt which, in Germany, came chiefly from the Carpathian Mountains, Transylvania, the Tyrol, and Poland. Rock and sea salt were still listed separately in the 1833 chemical-pharmaceutical handbook but, as from 1850, the origin of the salt was no longer specified. 

The pharmacists of the 19th century recommended internal use of salt against digestive upsets, goitre, glandular diseases, intestinal worms, dysentery, dropsy, epilepsy, and syphilis. Externally applied salt (e.g. cold or warm hip-baths) was said to be locally stimulating but acerbic to skin and mucous membranes at high doses. External application was advised in cases of rash and swelling and, in ophthalmology, to drive off stains and stain-obscurations of the cornea. A clyster (enema) of salt was even supposed to work for patients who were "seemingly dead and apoplectical". 
 

Salt in encyclopaedias and popular medicine in the 18th and 19th centuries

The encyclopaedias of the 18th century published extensive treatises on salt, in particular rock and sea salt, and referred to current knowledge on the healing powers of salt. A particularly infamous book was the Dirty Pharmacy by Paulini (1734) which held a collection of the nastiest imaginable mixtures for diseases of all kinds. Salt was a frequent ingredient. For instance, red watering eyes could be treated by covering them with a mush of fresh manure from a black cow, beer-vinegar, and half a knife's tip of salt. 

Medical practitioners of the 19th century paid particular attention to the effects of natural salt. In 1860, in eastern Bavaria, a sodium chloride solution was used as a compress against inflammation. Further west, inflammations of the belly button of children were washed with salt water. Warts were removed by spreading the juice of a snail that had been sprinkled with salt. Hot foot-baths containing salt and ashes were used to alleviate headaches. Burns were treated with brandy, vinegar or salt water.
 

Salt in 20th century medicine

As indicated above, salt was an important ingredient of remedies in Europe, on a par with natural products such as herbs, until the late Middle Ages. From then onwards, it became an item in the medicine chest of popular rather than academic medicine. It was not until spa therapy gained popularity in the 19th century that its healing powers gradually began to be investigated scientifically and not until the 1950s that its effects were studied in any detail.

Today, salt is a natural healing principle used in the form of inhalations, salt-water baths and in drinking-therapy. An important discovery of 20th century medicine is that salt water - in the form of an isotonic sodium chloride (saline) solution - has the same fluid quality as blood plasma. This has led to the use of salt solutions as intravenous infusions. However, salt solutions are also used subcutaneously, intramuscularly, as an enema or externally. 

Infusing saline

In 1832, the English doctors R. Lewins and T. Latta used a sodium chloride infusion successfully against cholera for the first time. Nowadays, isotonic sodium chloride solution (saline) has many uses:
- as a "replacement fluid" in emergencies. Saline can temporarily replace large amounts of lost blood and thus often saves the lives of accident victims. It can palliate prolonged loss of gastric juices.
- as a "tool and washing liquid". Chilled saline is used to determine cardiac output per minute, for medically founded forced drainage, to wash red blood cells for blood transfusions, and, at body temperature, to irrigate organs (e.g. gastro-intestinal tract, bladder).
- as a "carrier" solution for drugs.


From applying salt to bathing in salt 

Our journey through history has revealed that the antiseptic action of salt on the skin and mucous membranes has been known for a very long time. Scientific studies have now confirmed the effectiveness of salt therapy in several indications. The antiseptic and bactericidal qualities of dental salt (sea salt) help remove plaque which is a cause of gingivitis and caries. Salt is being increasingly used as support treatment for skin diseases. Chronically inflamed skin is treated with medical bath salt from the Dead Sea (d) or table salt. The salt peels off dandruff, reduces inflammation, itching and pain, and helps regenerate the skin. Salt-baths are frequently used to treat psoriasis, atopic dermatitis, chronic eczema as well as arthritis. Sometimes (as in psoriasis), this therapy is followed by ultraviolet light radiotherapy under strict medical control so that the combination of salt water and UV light does not expose patients to an increased risk of skin cancer.

The ancient Greeks had already recommended seaside health resorts to cure skin diseases and Paracelsus mentioned the effectiveness of "salt brine". Sea-water baths later led to salt-water baths in regions closely linked with the extraction of salt (salt mines, springs and works) but it was not until 1800 that doctors from the German town of Bad Nauheim introduced a methodical salt-bath therapy (6). They tried to obtain scientific evidence for claims regarding the healing effects of the waters. Current medical indications for salt-bath therapy rest, as a matter of principle, on the empirical traditions of centuries. They include support treatment for skin diseases due to the anti-inflammatory action of salt. Patients suffering from rheumatic conditions often experience relief from joint pain when moving about in a salt bath.

Finally, common or Dead Sea salt can be used as an additive especially in body care products (ointments, shampoos, gels, washes and body lotions).

Inhaling salt

Steam from salt water is inhaled in chronic diseases of the upper and lower respiratory track (pharynx, paranasal sinuses, and bronchial tree) or to ease the discomfort of a common cold. Let's not forget that Hippocrates had already recommended this treatment! The age-old method is to heat a salt solution to obtain steam but modern ultrasound atomising can now transport minute salt particles directly to tiny bronchia. The main effects of salt on the bronchial system are to stimulate secretion, loosen and help eliminate viscous secretions, inhibit inflammation, reduce irritation causing cough, clean the mucous membrane of the kinocilium, and contract (bronchoconstriction) or extend (dilatation) the respiratory ducts.

Drinking salt water

Salt water when drunk has an expectorant effect in the stomach and increases gastric juice secretion. It raises the level of stomach acid, hastens its production, impedes or stimulates stomach motricity and emptying-rate (depending upon the salt concentration), increases the secretion of the pancreas, and at higher salt concentrations stimulates the formation of bile acids.

Salt as a vector

Rock salt is of higher purity than sea-salt which can be contaminated with many minerals and other substances. Some of these contaminants, such as iodine, can be beneficial to health. Iodine deficiency is a major health risk. It gives rise to a thyroid gland disease characterised by hormonal disturbances causing cretinism and by a goitre which can be so large that it may blocs airflow through the throat or reach externally right down to the collar bone (7). Goitre used to be endemic in regions far from the sea such as the Alps but was rarely encountered in countries of southern Europe bordering the Mediterranean. Nowadays, Germany is the only industrial nation where goitre due to a lack of iodine is still common. This is because, despite the known health risk, part of the German food industry still uses the cheaper iodine-free salt for economic reasons. No legal measure makes the use of iodised salt compulsory in Germa ny. The health authorities must rely on public information campaigns promoting the benefits of salt with iodine.


Homeopathic salt

N. H. Schüßler (1821–1898), a German doctor, developed a special "biochemical" therapy based on 12 mineral salts which he considered crucial for cell function. This therapy is still used today. For Schüßler, health resulted from a balance among these salts, disease from a disequilibrium. Common salt (sodium chloride) was one of his 12 salts. He administered the salts in homeopathic doses in an extremely wide range of indications (anaemia, loss of appetite, loss of weight, common cold, stomach and intestinal disorders, watery diarrhoea, constipation, haemorrhoids, rashes, rheumatic troubles, headaches, fatigue) and externally against lip blisters, acne, comedo, skin fungus and sores.

 

A flip side to the coin?

In the Middle Ages, the School of Salerno warned against the excessive use of salt (see above). The subject of excessive salt use has been a matter of great controversy over the last three decades. Scientific medicine has found that a high salt intake from food, especially by people with an inherited sensitivity to salt, might increase the risk of cardiovascular disease (CVD).Extensive studies have indicated that too much salt in food may lead to arterial hypertension. There are those who forbid the addition of any salt at all to food and those who suggest that consumption should be limited to around 5 or 6 grams a day. There are epidemiological studies that indicate that populations such as the Japanese who consume vast amounts of salt have a high incidence of CVD but no direct causal link has yet been definitively established between salt consumption and high blood pressure. 

The cumulative past experience of our human ancestors and an increasing volume of current scientific evidence indicate that salt is a major life-preserving substance and effective healing principle. As often, therefore, the question is one of balance. When do possible health risks override the beneficial and vital effects of an adequate salt intake? The answer probably depends on the individual (e).

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Notes

(a) Science and medicine have tried to define the precise roles of salt in the healthy and diseased human organism. Blood, sweat, and tears all contain salt, and both the skin and the eyes are protected from infectious germs by the anti-bacterial effect of salt.
When salt is added to a liquid, particles with opposite charges are formed: a positively charged sodium ion and a negatively charged chloride ion. This is the basis of osmosis which regulates fluid pressure within living cells and protects the body against excessive water loss (as in diarrhoea or on heavy sweating). 
Sodium and chloride ions, as well as potassium ions, create a measurable difference in potential across cell membranes. This ensures that the fluid inside living cells remains separate from that outside. Thus, although the human body consists mainly of water, our "inner ocean" does not flow away or evaporate.
Sodium ions create a high pressure of liquid in the kidneys and thus regulate their metabolic function. Water is extracted through the renal drainage system. The body thus loses a minimal amount of essential water. Out of 1500 litres of blood which pass daily through the kidneys, only about 1.5 litres of liquid leave the body as urine. 
Salt is "fuel" for nerves. Streams of positively and negatively charged ions send impulses to nerve fibres. A muscle cell will only contract if an impulse reaches it. Nerve impulses are partly propelled by co-ordinated changes in charged particles.

(b) According to modern scientific research, salt does indeed have weak disinfectant properties when applied topically.

(c) Inhaling steam from salt water has become an established treatment for acute and chronic respiratory diseases in spa-, balneo- and thalasso- therapies

(d) The mineral composition of Dead Sea salt is slightly different from that of common sea salt . Dead Sea salt is considered to be particularly useful in chronic skin diseases such as psoriasis.

(e) I acknowledge with thanks Johanna S. Gordon's help in translating the German draft of this article.

 

References

1. Cirillo M, Capasso G, Di Leo VA, De Santo NG. A history of salt. Am J Nephrol 14, 426-31, 1994.

2. Denton D. The hunger for salt. An anthropological, physiological and medical analysis. Springer Verlag, Berlin, 1982.

3. Ritz E. The history of salt - aspects of interest to the nephrologist. Nephrol Dial Transplant 11, 969-75, 1996.

4. Wormer EJ. Heilkraft des Salzes. Suedwest Verlag, Munich, 1995.

5. Wormer EJ. Salz in der Medizin. In: Treml M, Jahn W, Brockhoff E (eds.): Salz Macht Geschichte (Collection of essays and catalogue). Haus der Bayerischen Geschichte, Augsburg, 1995, p. 48-55

6. Porter, Roy (ed.). The medical history of waters and spas. Wellcome Institute for the History of Medicine, London 1990.

7. Merke F. Geschichte und Ikonographie des endemischen Kropfes und Kretinismus (History and Iconography of Endemic Goitre and Cretinism). Verlag Hans Huber, Bern, 1971.
 

Author: Eberhard J. Wormer