Hives , Can anyone explain the reason ?

Interesting that SueDonim mentioned overactive thyroid combined with stress.
I went through a period of getting outbreaks of hives (urticaria is the medical name) when my thyroid was overactive.
However, it can be very difficult to find the cause of allergies- easier to just treat with anti-histamines and soothing creams!

Bed bugs? My son came out in similar after a stay in a B & B abroad…?
No offence just a thought?

I have had Hives at stressful times in my life, but I also had Hives when on Morphine following a TKR, I dropped the Morphine and the rash went. Its a horrible thing to have and you have my sympathy

Look like hives to me - unlikely to get bedbugs in hospital especially on a surgical ward.

Did it start on the leg which had the TKR? Just wondering if something used on the op. site triggered an all-over allergic response?

I had this following my bilateral total knee replacement. It was all over my legs. Chronic itching. At the time I put it down to the laundry powder that the sheets had been washed in at the clinic where I rehab'd
It sounds like you are at home but just mentioning in case. I hope they go quickly as the TKR recovery is quite enough to contend with

I had exactly the same last year. It started on my arm and within 2 days I was covered from head to foot! GP put me on antihistamines but they didn’t help at all. I tried E45 itch cream, which did ease the itching a bit but the rash was no better. After 2 weeks I was getting desperate and willing to try anything. I then remembered I had some prickly heat powder tucked away in the cupboard, so at bedtime I stripped my clothes off and covered myself in prickly heat powder (not a pretty sight), I continued this for a couple of days and hey presto it worked! My rash was put down to stress after just going through the death of my brother.
Hope your rash soon clears up.

It looks like giant uticaria a common allergic reaction to medication. I suggest you find out which medication before it develops into a more serious allergic reaction i.e anaphylaxis.

I had it once from stress.

Picture looks like me when my chronic spontaneous urticaria was at its peak, it started in 2020 triggered by a couple of drug reactions, namely Riveroxban when I had a new hip in ‘ 19, that wore off, but then I was put on Ramipril for bp, and I’ve had urticaria since then. Initially my GP sent me to my local dermatology unit, quite frankly they were useless. I put up with it for a long time time, but then asked to be referred to Guys/St Thomases, were they have a specialist allergy department who are wonderful. I take 4 antihistamines a day plus other medications, I have non scented soap ointment for bathing plus cream which I apply morning and evening. I’ve had biologic injections last year, and am currently having more, as the effect wore off, however although I’ve only had one lot they’ve worked much faster, I have to have five more. My urticaria is autoimmune, no reason at all for it. Good luck!

I've had them a couple of times, years ago moving to a new office within the building I was already working in, old and Georgian it was a winter's day and cold so an electric fire was put on. I came out in red spots all over, "you better go home" said my boss "looks like German measles", I went to the doctor who thought the same, did some blood tests, transpired it wasn't. Whilst waiting for the results got signed off for a week.

Another time one of those unusually hot early Spring days. I found myself with others sitting on grass, again came out in hives, I didn't think it was anything else that time. I wondered perhaps the reason being whether it hadn't had the gradual getting to know the greenery as Spring slowly merges into Summer, it was a heatwave and the introduction immediate, "hello grass" after having not being around it for quite a few months. Who knows! That was all before the advent of Dr Google, so my own theory. In both cases my rash disappeared fairly rapidly.

I hope your rash clears OP it does look like an allergy.

Peculiar stuff skin

Just wondered why they put you on blood thinners...is it a precaution for a blood clot, post op? I'm on them for Atrial Fibrillation. They clearly recognise the distress and pain to give oral morphine. I don't know what TKR is?

Oh dear poor Nana I’ve had this snd it’s very unpleasant and. I think you’ll find this is an allergic reaction to an antibiotic.
I was given antibiotics to treat s bladder infection and like you I was covered in a rash, all over, and I was terrified.
I phoned our NHS helpline in the middle of the night and was advised to take 2 antihistamine tablets right away and one in 4 hours then go to my doctor as soon as possible.
Thankfully the rash was starting to ease but I saw my doctor snd he said I had been given the right advice and stop taking the antibiotics and he gave me another one and I had to carry on with the antihistamine for a couple of days and he gave me a prescription for both tablets and cream. Within 24 hours the rash had eased and I did feel much better. I had a call from the doctor and was told to make sure I was never prescribed the antibiotics again and I was given an allergy alarm bracelet and it was on my health records that I was allergic. Many times since I’ve had to say I’m allergic and luckily I’ve never had another problem. I do hope yours clears up soon and you feel better.

Plevey08 Total Knee Replaced

Ta very much

I had exactly this rash/hives which got worse and worse over 24 hours, until I eventually collapsed with extremely/dangerously low blood pressure. Turned out it was from newly prescribed Naproxen, which were supposed to be "better" than ibuprofen or diclofenac which I had previously taken for arthritis. Was told that the allergic reaction was so bad it was no longer safe for me to take any NSAID (non steroidal anti inflammatory drugs). Rather a nuisance but would never risk it again!