# Epsom Salt? **URL:** \ **Category:** Factual Questions\ **Created:** [October 5, 2022, 9:21pm UTC](https://boards.straightdope.com/t/epsom-salt/972782 "2022-10-05T21:21:20Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![justmeetee](https://avatars.discourse-cdn.com/v4/letter/j/898d66/32.png) [@justmeetee](https://boards.straightdope.com/u/justmeetee)\ **Post date:** [October 5, 2022, 9:21pm UTC](https://boards.straightdope.com/t/epsom-salt/972782/1 "2022-10-05T21:21:20Z")
I’m constipated today and using epsom salt as a laxative. Just drank another dose and I see on the carton a use by date of January 2117. It’s salt. Can it really “expire” ? I saw an ad for 10,000 year salt with an expiration date and it seemed odd. How does something 10,000 years old now expire in 3 years? I figured it was just Gubbermint rules said you can’t sell anything without an expiration date. So can epsom salt ACTULLY expire? ---
**Author:** ![BippityBoppityBoo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bippityboppityboo/32/5745_2.png) [@BippityBoppityBoo](https://boards.straightdope.com/u/BippityBoppityBoo)\ **Post date:** [October 6, 2022, 12:44am UTC](https://boards.straightdope.com/t/epsom-salt/972782/2 "2022-10-06T00:44:05Z")
> [@justmeetee](#): > > So can epsom salt ACTULLY expire? This would be a really good question to ask a pharmacist. We have one or two on the Board, hopefully one will stop by. Here’s what [www.primalsurvivor.net](http://www.primalsurvivor.net) says: ….Although Epsom salt comes with an expiration date, this purely because it’s a legal requirement. **Most manufacturers say it’s perfectly safe to use long after this date has passed** , although it may start to clump or get hard after that point.Sep 6, 2021… ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [October 6, 2022, 1:49am UTC](https://boards.straightdope.com/t/epsom-salt/972782/3 "2022-10-06T01:49:15Z")
> [@BippityBoppityBoo](#): > > this purely because it’s a legal requirement. Drugs require an expiration date but I don’t think Epsom salts are considered a drug. ---
**Author:** ![needscoffee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/needscoffee/32/1076_2.png) [@needscoffee](https://boards.straightdope.com/u/needscoffee)\ **Post date:** [October 6, 2022, 1:52am UTC](https://boards.straightdope.com/t/epsom-salt/972782/4 "2022-10-06T01:52:41Z")
When I worked for a gourmet salt/sugar company, we had to put an expiration date of no more than 5 years on them as requirement of Amazon’s in order to sell as an Amazon vendor. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [October 6, 2022, 2:15am UTC](https://boards.straightdope.com/t/epsom-salt/972782/5 "2022-10-06T02:15:05Z")
IAMNAD and this is only from a chemistry perspective. Epsom salt is magnesium sulfate hydrated to its fullest MgSO4.7H2O. Magnesium sulfate is hygroscopic i.e. absorbs water from air (like silica gel). For the unhydrated form, it is hard to weigh a specific amount of Magnesium since you do not know how much water it has absorbed, therefore the hydrated form is used. But even the hydrated form clumps up over time thereby telling you that it was not 100% hydrated. So old epsom salt (especially if it is clumped up) has more water in it (less potent). I have also worked with Sulfate Reducing Bacteria in Gypsum (Calcium Sulfate) - these are some freaky anaerobic bacteria that do not use carbohydrates for energy but sulfur. They are usually found around volcanoes or gypsum plants. They will make your epsom salt smell like rotten eggs. The chances of that happening is extremely low and you are probably okay with using it. ---
**Author:** ![nearwildheaven](https://avatars.discourse-cdn.com/v4/letter/n/90db22/32.png) [@nearwildheaven](https://boards.straightdope.com/u/nearwildheaven)\ **Post date:** [October 6, 2022, 4:11am UTC](https://boards.straightdope.com/t/epsom-salt/972782/6 "2022-10-06T04:11:11Z")
2117? Did you actually mean to say 2017? If it looked and smelled okay (I would hesitate to say that it tasted okay!), it shouldn’t be a problem. The expiration date is mainly for stock rotation. ---
**Author:** ![WellHelloThere](https://avatars.discourse-cdn.com/v4/letter/w/9dc877/32.png) [@WellHelloThere](https://boards.straightdope.com/u/WellHelloThere)\ **Post date:** [October 6, 2022, 7:28am UTC](https://boards.straightdope.com/t/epsom-salt/972782/7 "2022-10-06T07:28:37Z")
I used it to soak my feet. It did nothing. I think you should not eat it ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [October 6, 2022, 7:40am UTC](https://boards.straightdope.com/t/epsom-salt/972782/8 "2022-10-06T07:40:23Z")
Expiry dates on any packaged goods exist in part to assist with stock rotation - which in turn is not necessarily anything to do with the ‘expiry’ of the product, but rather the packaging. The longer a package sits on the shelf, the less saleable it tends to look. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [October 6, 2022, 7:36pm UTC](https://boards.straightdope.com/t/epsom-salt/972782/9 "2022-10-06T19:36:14Z")
My doctor told me once that the US Army had studied antibiotics and concluded that they are still active after 15 years. Since I had had several UTIs, he prescribed an antibiotic, just in case and told me to replace it after 15 years. I somehow doubt I will be around in 15 years. ---
**Author:** ![Treppenwitz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/treppenwitz/32/3445_2.png) [@Treppenwitz](https://boards.straightdope.com/u/Treppenwitz)\ **Post date:** [October 6, 2022, 8:10pm UTC](https://boards.straightdope.com/t/epsom-salt/972782/10 "2022-10-06T20:10:53Z")
> [@CookingWithGas](#): > > Drugs require an expiration date but I don’t think Epsom salts are considered a drug. Here’s the US patient information for (medical) Epsom Salts: > **[Epsom Salt Uses, Side Effects & Warnings](https://www.drugs.com/mtm/epsom-salt.html)** > > Physician reviewed Epsom Salt patient information - includes Epsom Salt description, dosage and directions. Obviously I don’t know what grade of Epsom Salts @justmeetee was using. But here’s at least one explanation of why there’s an expiration date. That compendial entry from [drugs.com](http://drugs.com) lists side effects and warnings. I presume they still provide this as a leaflet in the pack. These leaflets are routinely reviewed and updated, one of the functions of this being _to include new side effects and warnings as they come to light_. The thinking in re very old stock is, even if a drug doesn’t decompose, a paper leaflet which accompanies it can be so out of date as to be dangerously misleading OK, so that reflects a general approach which may not be that necessary for something like Epsom Salts - but general approaches are applied generally, so it’s not a surprise that there is an expiry date. And yeah, you can find an up to date leaflet on line easily enough. But still, there’s a potential (maybe “theoretical” is a better word) liability issue here - for something that is intended to be used as a medicine. j. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [October 8, 2022, 12:46am UTC](https://boards.straightdope.com/t/epsom-salt/972782/11 "2022-10-08T00:46:46Z")
> [@Hari\_Seldon](#): > > My doctor told me once that the US Army had studied antibiotics and concluded that they are still active after 15 years. Be careful with tetracycline and similar antibiotics. They are harmful when they expire. ---
**Author:** ![nearwildheaven](https://avatars.discourse-cdn.com/v4/letter/n/90db22/32.png) [@nearwildheaven](https://boards.straightdope.com/u/nearwildheaven)\ **Post date:** [October 8, 2022, 3:10am UTC](https://boards.straightdope.com/t/epsom-salt/972782/12 "2022-10-08T03:10:46Z")
I hope it wasn’t tetracycline, because its 3-dimensional structure can change with time to a form that is toxic. (Stereoisomerism, to be exact) ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [October 8, 2022, 4:20pm UTC](https://boards.straightdope.com/t/epsom-salt/972782/13 "2022-10-08T16:20:54Z")
> [@am77494](#): > > Be careful with tetracycline and similar antibiotics. They are harmful when they expire. Did not know that about tetracycline. You shouldn’t have expired tetracycline sitting around anyway since you are supposed to finish the entire prescription, and it’s always unwise to use old medication after self-diagnosis. All that being said, no doubt people will do it anyway. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 8, 2022, 4:36pm UTC](https://boards.straightdope.com/t/epsom-salt/972782/14 "2022-10-08T16:36:52Z")
Most things that have expiration dates, it’s just about marketing. There are plenty of food products that really would stay good indefinitely, except that people would be suspicious if you told them that (“What are they putting in that stuff to make it last so long!?”), so they stick on a meaningless expiration date a few years in the future, instead. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [October 9, 2022, 4:45pm UTC](https://boards.straightdope.com/t/epsom-salt/972782/15 "2022-10-09T16:45:05Z")
Even something like Himalayan salt could have an expiration date for additives breaking down, moisture or other contaminant intrusion, or even chemical reactions that wouldn’t happen in the mine where it’s produced. @Chronos’s “it’s just marketing” statement is pretty hyperbolic, because most things with expiration dates do actually spoil/rot/break down. Think meat, produce, bread, dairy. Dried beans, white rice, honey, liquor, and bullion cubes don’t make up a significant portion of foods with expiration dates. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 9, 2022, 5:04pm UTC](https://boards.straightdope.com/t/epsom-salt/972782/16 "2022-10-09T17:04:08Z")
Even in those foods that do go bad, the expiration date isn’t a very good guide for when it’ll happen. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [October 9, 2022, 5:22pm UTC](https://boards.straightdope.com/t/epsom-salt/972782/17 "2022-10-09T17:22:43Z")
Very true, especially if you freeze something whose expiration date is based on refrigerating, like meat for example. ---
**Author:** ![nearwildheaven](https://avatars.discourse-cdn.com/v4/letter/n/90db22/32.png) [@nearwildheaven](https://boards.straightdope.com/u/nearwildheaven)\ **Post date:** [October 10, 2022, 1:40am UTC](https://boards.straightdope.com/t/epsom-salt/972782/18 "2022-10-10T01:40:41Z")
I often eat yogurt that’s several MONTHS beyond its expiration date. I mean, what is yogurt anyway, but preserved milk? I can only think of a couple of times where I got a yogurt cup that looked and smelled bad, and those were within dates. ---
**Author:** ![needscoffee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/needscoffee/32/1076_2.png) [@needscoffee](https://boards.straightdope.com/u/needscoffee)\ **Post date:** [October 10, 2022, 1:44am UTC](https://boards.straightdope.com/t/epsom-salt/972782/19 "2022-10-10T01:44:17Z")
> [@jjakucyk](#): > > Even something like Himalayan salt could have an expiration date for additives breaking down, What additives could break down? This is millions-years-old salt. Preserved in salt. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [October 10, 2022, 2:04am UTC](https://boards.straightdope.com/t/epsom-salt/972782/20 "2022-10-10T02:04:16Z")
If it’s an additive then by definition it wasn’t in the salt when it was mined. Usually that’s anti-caking agents (calcium silicate), and potassium iodide, in which case it will also have a little sugar (dextrose) to prevent oxidation of the potassium iodide. It’s unlikely Himalayan salt would have those additives because it’s not packaged finely ground, but there’s nothing stopping their use either.