[Fleecewife]

OK I'm an eegit, but I really didn't know about this.  We had two burst hot water bottles within a couple of weeks, so they were banned from our bed.  However, our bedroom is freezing, so I wanted something.  Those microwaveable wheat bags seemed to be the answer.
All seemed well at first, but then I woke up one morning with a sore foot, which was red and swollen.  Mmm, it went away on it's own after about a week though so I didn't think much more about it.  Then earlier this week it happened again.  At first it was a small area affected, on the other foot, but gradually the swelling has spread to my whole foot, which is tight and red, and a bit sore.
So I thought about the wheat bag - it should be at a low temp if microwaved for the correct time, on the correct power, but clearly mine was causing some sort of damage.  I began to wonder about the time my skin was exposed to the heat - both times I had slept very deeply, and I dragged up the expression 'low temperature burns' from the depths of my memory.  Google is very helpful at answering obscure questions, so now I know that not only are low temp burns a fact but they are frequently caused by......microwaved wheat bags, and especially so on the feet.  Apparently long exposure to a heat source above 44C can cause a low temp burn, which can be quite deep.
There are various research studies about this very subject, so why on Earth are wheat bags sold without giant warnings all over them?

So, my advice (to myself) is to heat the thing for only half the recommended time, and to kick it out of the bed before I go to sleep.

It's snowed this evening, so covering my burnt foot with snow is lovely - now that I've stopped 

[paddy1200]

Any temperature above normal body temperature can cause burns if applied for long enough. Same goes for below normal temp.
Hot water bottles should not be applied directly to the skin, much the same as frozen peas for a strain/sprain.
Burns are caused by contact with extremes of temperature, hot or cold, which cause tissue destruction.

[SallyintNorth]

Would it help to make the wheatie hottie a woolly jacket?  I always have a jacket on my (water) hottie, precisely because otherwise it burns.  And added bonus, the wool acts as insulation, so keeps it warm for longer.

[Buttermilk]

Also older wheat bags are worse as they can ignite.  The wheat dries out with use and becomes flamable.

[claire]

I always shake them about after heating... to even up the heat... microwaves always create a hot spot somewhere... and I like the idea of a cover.. I would always have a hot water bottle covered so imagine the same for wheat bags would be a good idea... and don't put the cover in the microwave.

[Womble]

So, my advice is.......... to kick it out of the bed before I go to sleep.

That's what Mrs Womble does to me once I've warmed her up, and hence outlived my usefulness! 

[Cosmore]

When I was a mere lad many years ago (violin playing in background) and slept in an unheated bedroom with single glazing and the frost made paisely patterns on the inside of the glass, my dear mother gave me a stone hot water bottle (Boots own from probably the 1930's!) but it was always wrapped up in a thick towel first so as not to cause burns (and to soak up any leakage from the stone screw top sealed with a rubber washer). It worked brilliantly, the worst part was getting up in the mornings shivering and seeing your breath hanging in the air!

[Marches Farmer]

Our how about one of those copper bed warming pans on a long wooden stick that the house varlet pushes around between the sheets to warm the bed through before you get into it ....?

[waterbuffalofarmer]

or..... you could just simply buy an electric blanket 

[Fleecewife]

I hate electric blankets WBF.  When I was young some friends burned their house down from using one - must have been faulty but I wouldn't ever sleep in a bed with one - I'd not sleep for worrying I was about to be incinerated     I like the idea of the warming pan (although you need hot coals and our wood burner isn't always alight and you need a servant to swish them around the bed  ).  I am old enough to remember them, and the stone bottles (in fact we still have one in the attic), and the Jack Frost on the windows, the frozen potty and all 
But now we're getting on we really love being WARM, but also safe.
My wheat bag does have a cover, but that's a great idea Sally to knit one.   We always had covers on the hot water bottles - Mr F's is Babe  and he's most annoyed he's not allowed to have it any more   

Today my foot is a bit worse, with oedema spreading up my leg, but I don't think it's bad enough to worry about.  It's a great excuse though to sit about with my leg up.  I can't spin, but I can knit.......

So thank you all for the info and ideas.   And Womble, you always make my day with those comments you pop in   

[Penninehillbilly]

the worst part was getting up in the mornings shivering and seeing your breath hanging in the air!

Been there, had the chilblains  . it was the ice on the sheet from my breath that I remember. That was at Moss Side Croft, New Deer.

[doganjo]

Bedsocks? 

[devonlady]

Ma would put house bricks in the range oven, wrap them up in pieces of old blanket and put them in our beds. They were lovely and warm but too uncomfortable to cuddle up to, we had sisters for that! A bit of a shame maybe that todays children won't see "Jack Frost" windows.

[Marches Farmer]

They might if they lived in our house - why change a 500 year old tradition, eh?

[Fleecewife]

Bedsocks? 

Yep, I already wear those