Table salt may contain additional unwanted ingredients. Only pure NaCl or minerals found in sea water should go into such a solution. But food industry is usually allowed to add much more.
Nasal irrigation salt needs just to be NaCl used in isotonic concentration. The indian tradition is ancient and based on water from rivers, which is not isotonic and now often contaminated.
**Clean** (i.e. lower salt concentration; but if the water supply isn't safe also meaning: sterilised?), potable/drinking tap-water works as well, but appears much harsher than needed. It is uncomfortable. So isotonic solutions are clearly preferable. Too low salt concentrations let the cells swell up, too high a concentration dries them out and will lead in the mid term to much worse results. The added salt is not needed for the practice , but beneficial if the concentration is hovering around 0.9%.
One can use regular salt for that. As long as it's pure NaCl. And one may be 'lucky' in using all other forms of table salt. *But* regular commercially sold table salt is usually *not* just NaCl!
**What is neti-salt?**
First link to vendor appearing in a websearch:
> Ingredients: Pharmaceutical grade sodium chloride (99.99%) USP.
> Directions: Place a heaping 1/4 teaspoon in your Neti Pot and add warm water.
Whether sea salts minerals are in there as well is not really that much more beneficial, but when it's regular "table salt" then most jurisdiction allow a lot of other ingredients in it that you do not want in your nose pr on your mucus membrane.
**Regular kitchen table salt can be used but is *not recommended* because of all the additives.**
Apart from possible adulterations when using "funny" salts ('Himalaya' etc) [allowed anti-caking agents for example are:][1]
341 tricalcium phosphate
460(ii) powdered cellulose
470b magnesium stearate
500 sodium bicarbonate
535 sodium ferrocyanide
536 potassium ferrocyanide
538 calcium ferrocyanide
542 bone phosphate (i.e. Calcium phosphate)
550 sodium silicate
551 silicon dioxide
552 calcium silicate
553a magnesium trisilicate
553b talcum powder
554 sodium aluminosilicate
555 potassium aluminium silicate
556 calcium aluminosilicate
558 bentonite
559 aluminium silicate
570 stearic acid
900 polydimethylsiloxane
Some of these are listed in the Eu as E170, E504, E535, E536, E551, E559…
> [Table salt][2]
> Table salt is sodium chloride combined with iodine sources (for nutrition), stabilizers for the iodine, and anti-caking compounds to make it pour by preventing it from absorbing water from the air.
So supermarket bought regular table salt can be quite a bit too irritating for a nasal irrigation. Depending on jurisdiction not all ingredients have to be listed on table salt.
> Nasal irrigation is based on warm saline solution, i.e. salt dissolved in lukewarm tap water. ... However, chemical anti-caking (aka “free-flowing”) additives used in common table salt (e.g. sodium silicoaluminate) produce an unpleasant burning sensation in the nose and are not advised medically or by Yoga instructors.
> <sub>–– [The problems of salt for neti - NetiNext][3]</sub>
> anti-caking agents or preservatives (these can be irritating to the nasal lining)
<sub>–– [SALINE SINUS RINSE RECIPE 2019 American Academy of Allergy, Asthma & Immunology.][4]</sub>
With just a little chemistry knowledge anyone can conclude: among other things nasal irrigation is used for reducing mucus viscosity. This is clearly not an outcome achieved if adding bentonite into a solution for the nasal cavity. While listed as [non-toxic non-irritating][5], bentonite is used as cat litter, and hence it does in the nose what it does in the litter box: increases viscosity of mucus. This effect is there for all anti-caking agents. Some are directly irritating the membranes, all are doing the opposite of what one wants to achieve.
For the US salt for use in organic products:
> Are additives allowed in the salt I use in my organic products?
Though salt and sea salt are allowed in all categories of organic products, anti-caking/free-flow agents and whiteners are generally not allowed in these products. Common anti-caking/free-flow agents that are not allowed include:
>• Calcium silicate
• Ferric ammonium citrate
• Sodium ferrocyanide
• Magnesium silicate
• Magnesium carbonate
• Propylene glycol
• Aluminum calcium silicate
• Sodium aluminosilicate
> [USDA organic regulations (PDF)][6]
In Europe, only [E170 Calcium carbonate][7] is allowed in salt for organic uses.
Ordinary table salts may still contain (sodium and magnesium carbonate (E 500, E 504), sodium-, potassium- and calcium ferrocyanides (E 535, E 536, E 538), [silicon dioxide][8], calcium- and magnesium silicates (E 551 – E 553), [iron][9] [tartrate][10] (E 534). Aluminium salts are no longer allowed in Europe as an additive, but can be a [found][11] in [some][12] [salts][13].
[Additives List, E numbers in Numerical Order, Food Safety of Ireland, 2019.][14]
---
Further regular nasal irrigation isn't very well supported for most use case anyway:
Karen Head, Kornkiat Snidvongs, Simon Glew, Glenis Scadding, Anne GM Schilder, Carl Philpott, Claire Hopkins: "Saline irrigation for allergic rhinitis", in: Cochrane Database of Systematic Reviews. No. 6., 22. June 2018. doi:10.1002/14651858.CD012597.pub2
[Saline nasal irrigation: Its role as an adjunct treatment][15]
Disclaimer:
ill people or those with recent surgery as well as extra paranoid germaphobes might want to boil the water before use, to kill any of the germs potentially present in any water, then wait until it reaches body temperature.
***If* the municipal water supply is *reasonably clean* this is not necessary for healthy adults.** People in third world countries like the USA may want boil the water for all the reasons above anyway. In regions with sane safety standards regarding the water supply that are actually enforced, many [doctors often explicitly deny the need to boil water first.][16]
Main sources for bacterial contamination are preparing a too large portion of solution and letting it sit and the pots used themselves:
> Although common and frequently based on potentially dangerous bacteria, contamination is considered a false problem by some experts. They think that the nasal cavity is naturally full of bacteria and the addition of new pathogens is not clinically relevant.
> The problem of sterility of the solutions and devices has been debated. **Solutions are at risk of contamination when large volumes of solution based on distilled water, bottled water, or boiled water are prepared at home, maintained in containers** and used each time when NI is needed by withdrawing the required amount of liquid. Devices can be contaminated when they are continuously used without adequate cleaning. Lee et al. reported that **after one and two weeks of use, irrigation bottles** used by adults undergoing endoscopic sinus surgery that were washed with hot soapy water after each use **were found to be contaminated by a large spectrum of bacteria, including Pseudomonas aeruginosa, Serratia marcescens, Proteus mirabilis, and Staphylococcus aureus**. Similar findings were reported by other authors and, because in many cases contaminating bacteria were the same as those that could cause acute rhinosinusitis, it was suggested that the main source of device colonization was the sinonasal cavities. The risk of contamination seems independent of the type of device. Additionally, the use of a one-way valve irrigation bottle, theoretically capable of reducing the risk of reflux of contaminated solution in the device, was found to be practically ineffective. In contrast, contamination seems to be influenced by the composition of the solution. It was shown that acidic, isotonic saline solutions were more frequently associated with bacterial contamination probably because some of the most common contaminants grow optimally in similar environmental conditions. Finally, contamination was found more frequently with longer durations of NI use. With some exceptions, studies have reported that both bottles and bulb syringes were contaminated after one to two weeks of use in approximately 25% of the cases and in 45% after four weeks.
> <sub>–– Nicola Principi & Susanna Esposito: ["Nasal Irrigation: An Imprecisely Defined Medical Procedure"][17], Int J Environ Res Public Health. 2017 May; 14(5): 516. doi: 10.3390/ijerph14050516 PMCID: PMC5451967
PMID: 28492494</sub>
[1]: https://en.wikipedia.org/wiki/Anticaking_agent
[2]: https://sci-toys.com/ingredients/table_salt.html
[3]: https://www.erp4it.com/netinext/2011/04/the-focus-of-this-post-is-on-neti-as-a-regular-practice-in-the-american-bathroom-and-the-related-economic-and-usability-issu.html
[4]: https://www.aaaai.org/conditions-and-treatments/library/allergy-library/saline-sinus-rinse-recipe
[5]: https://digitalfire.com/4sight/hazards/ceramic_hazard_bentonite_toxicity_31.html
[6]: https://www.ams.usda.gov/sites/default/files/media/7%20Salt%20and%20Preservatives%20FINAL%20RGK%20V2.pdf
[7]: https://en.wikipedia.org/wiki/Calcium_carbonate
[8]: https://en.wikipedia.org/wiki/Silicon_dioxide
[9]: https://en.wikipedia.org/wiki/Ferrous_tartrate
[10]: https://en.wikipedia.org/wiki/Tartrate
[11]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2782734/
[12]: https://www.nutritionmyths.com/aluminum-in-table-salt/
[13]: https://timesofindia.indiatimes.com/life-style/health-fitness/photo-stories/table-salt-can-be-poisonous/photostory/64385362.cms
[14]: https://www.fsai.ie/faq/additives/list.html
[15]: http://www.cfp.ca/content/49/2/168.full.pdf
[16]: https://hals-nase-ohren.com/nasendusche-hno-nuernberg
[17]: https://dx.doi.org/10.3390%2Fijerph14050516