Idiopathic urticaria - sweat/heat allergy?

[ImSweetEnough]

I spent most of 2025 struggling with what I initially thought was eczema (diagnosed with chronic eczema in childhood). I am 55 now and am used to managing my eczema if and when I do experience a flare up. Over the years, mostly my hands and face have been affected, relatively mildly.

My GP thinks that what I am experiencing now is not eczema but some kind of allergy. I agree with this. Oddly, every area of my skin except my hands, face and the soles of my feet is affected. It got very bad and I was prescribed Prednisolene, antibiotics and I now take 2 x antihistamines daily and have mild topical steroid (no lectures about steroid use required, thank you).

Now that my skin is in better condition, I have been able to try and think about what the cause could be and it seems that my own body heat and sweat are making me itch.

The intense itching usually starts just before bedtime when I am changing into my PJ's. I am not sweaty then but the itching starts. It is very intense and mostly my legs, back, stomach and my arms.

I have noticed at work if the heating is on too high, I begin to itch.

Last night I woke up sweating and itching. Heating is not on at night.

I have not had a period since the beginning of last year. Not sure when they stopped as up until February last year I was taking the mini-pill. The rash started before I stopped taking the pill as I wondered if stopping it may help.

The GP suggested a dairy or gluten allergy but the itching happens whether or not I have had milk or gluten that day. It does seem to start as soon as I get hot or perspire.

Any advise or can anyone relate to this?

Cholinergic urticaria. I have it

Thank you. Any tips on how to manage it? I feel like I need to go out at lunch and buy a water spray or something!

honestly? A dermatology referral
this is helpful as it lists the treatment options. I was on 4 Zyrtec daily but still unable to exercise or wear a coat and it’s been 30 years of it
now on Xolair injections which have been life changing

Thank you. My GP has referred me to dermatology.

Thank you for your reply and advise.

Xolair looks horrifying if they offer it you, I have no side effects at all from it! Apart from no hives

I had this as a teenager - came on when I was about 12, and probably only truly went in my early 20s. I have no idea what triggered it to come and go like that (i.e. at those ages) but I went to see the GP numerous times and was told it was heat triggered urticaria. Every PE lesson at secondary school I remember being covered in red itchy patches that had the raised little white lumps. I was told I could take antihistamines to help, but I don't think I ever did. Every time I got sweaty, I also got the rash. I remember being so anxious about it for years and that in itself became a problem, as the anxiety made me hot etc.

It went as an adult, and even though I'm still very heat intolerant (hot sweaty mess in my late 40s lol), it has never returned.

I have cold urticaria so I empathise. At one point mine was so bad I couldn’t even walk down the freezer aisle in the supermarket as I’d break out in hives. It’s controlled well with Fexofenadine but even on a cold morning, I can wake up and if a foot is out from under the covers, the itching has started. I take my anti hists as soon as I wake up (before I’m out of bed) and that helps.

I’m on dupixent and 40mg of certrizine a day. I still get hives from showering, sleeping, and various other things.

Things that help immensely:

• try to shower in cooler water no matter how frustrating - or occasionally accept the hives in exchange for a hot shower
• I wear bamboo pajamas and I only wear each pair once before washing in fragrance free detergent
• i have cooling sheets that I change frequently
• i use a weighted blanket to give me heft, but not actual warmth for sleeping.
• I have a fan positioned to blow directly on me as I sleep
• make sure there is no dust or grit in the bedroom that could cause physical skin irritation

.

Thank you all for the advise.

One more thing, keep ice packs in the freezer. They can stop hives unless you get cold induced hives. Also they trick your body into not itching so you don’t scratch and make them worse.

I could have written this post word for word down to the age, chronic eczema and times/ triggers of flare ups. In fact I genuinely checked the username and date to see if I’d written a post and forgotten about it!

I have a dermatology appointment coming up in February so I’m going to ask about the medications recommended here, so thanks for sharing. I’m currently on 180mg fexofenadine twice daily and I take them in bed first thing in the morning and last thing at night. I also use Synalar ointment and tachrolimus but the latter is unbearable when in the midst of a full flare up but useful if I can get in there early and has the added benefit of being steroid free. I have lots of empathy for you OP.

I had a reaction like this to fexofenadine. The first time I took it was when it was prescription only and I got it for going abroad to deal with the prickly heat, I took it daily for two weeks and my skin was an absolute mess. I blamed the heat/foreign water additives in the shower water/whatever detergent the hotel washed their bedsheets in. When it became available to buy over the counter I tried it again and my skin immediately started to break out so I stopped taking it and it cleared up. I'm fine with other antihistamines like loratidine and cetrizine hydrochloride.

Montelukast cured me of mine, I take fexafenadine 180mg but I saw an immunologist about 15 yrs ago who prescribed me Montelukast for my idiopathic urticaria and angioederma and it was transformative…I think it was all part of MCAS and thankfully is now well managed on these meds

We are obviously the same person because I am currently also taking 180mg Fexofenadine twice daily at each end of the day!

I like Protopic but, yes, the burning and itching.

My sympathies to you. It's so bloody frustrating and affects quality of life.

I do wonder if this strange flare/allergy is related in some way to hormones (GP laughed at the suggestion, despite plenty of articles online about itching being a symptom of peri/meno). But definitely there is a direct link between sweat/body heat = itch.

I would be interested in what your derm recommends, if you feel you can share. I hope they can get on top of this for you.

Yes, I will certainly share! I have been back and to with GPs for the past 18 months and they now think it’s all related to burnout and stress, which I can get on board with but don’t think it explains everything, especially the association with heat and sweat. I used to love summer and hot weather but now find it an ordeal, it’s so annoying. I hope they give me a miracle cure.

All the very best @MostlyGhostly! And thank you.

It feels a bit like looking for a needle in a haystack and you can't even get up to go to the haystack to start searching for the needle when you feel so awful. Hopefully the derm will help solve the puzzle and alleviate things for you long term.

I have an update: I have worked out that it was actually an intolerance to products containing paraffin. Because it puts a layer over the skin, it would cause intense itching when I did perspire even just a little.

@ImSweetEnoughI'm back too after my non-event trip to the dermatologist. I just got told to up my fexofenadine to 4 per day and that she would refer me to the urticaria specialist clinic and see what they say before even considering any next line treatment. The clinic was running very late and I got the impression they wanted me in and out ASAP. Please do let us know how your paraffin elimination goes over summer and whether cutting out products containing it helps with flare ups during the sweatier months

I’ve suffered from urticaria on and off throughout life but as I look back on it I see it’s usually a delayed reaction to a very stressful period. I think I was given some medication the first time it happened (about 45 year ago) but can’t remember what. I use one a day antihistamines now if I have a flare up

I had this suddenly onset from both hot and cold changes in temperature about 25 years ago. I saw a dermo and he gave me some bright pink antihistamines (sorry can't recall name) and it eventually went away. I still live in fear of it returning though.

Plus I have terrible trypophobia ad the hives would also send me off. Even looking at photos of them now makes me queasy.

I’ve had idiopathic urticaria since 2020, initially triggered by riveroxban after an operation, and then by ramipril. Mine is autoimmune, after a wait I saw useless dermatologists at my local hospital,I went back to my GPand asked to be referred to St Thomas hospital,they have an allergy clinic. I’m now on four antihistamines a day, and Montelukast and Famotodine. Last year I had a series of Omalizumab injections, which have helped somewhat, very little itching in the day,find the nights are the worst, I take ice blocks to bed in case the itching is bad. I have also been prescribed unperfumed cream to put all over morning and evening, plus a soap substitute. I also have a 2% menthol cream which is very soothing.

I am 60 and this cam out of nowhere 2 months ago.
I am not on any medication but follow an anti inflammatory diet as much as possible.

I can feel a prickle during the day around my face but its usually my body at night.
Last night was just awful.
I took two piriton when one wasn't enough.

I had eaten eggs with cheese and chilli last night so will avoid those for a bit.

Any food advice?