What it is
It is called acute when it has been present for under 6 weeks and chronic beyond that, and one group of patients has an inducible form brought on by scratching, pressure, heat, sweating, exercise, cold or water. Treatment rests on non-sedating antihistamines with the dose adjusted under supervision, a small and targeted set of tests rather than a broad allergy panel, and a clear written instruction about when a swelling needs emergency care instead of an appointment.
What this page covers
- Acute urticaria, with review of a possible drug, food or infection trigger — NSAIDs and antibiotics asked about directly
- Chronic spontaneous urticaria
- Inducible (physical) urticaria: dermographism, delayed pressure, cholinergic and heat-triggered, cold, exercise-induced and aquagenic forms
- Second-generation antihistamines and supervised up-dosing, with the effect on driving discussed
- A targeted workup, including thyroid autoimmunity, in place of broad allergy panels
- Referral for omalizumab or other second-line therapy where symptoms persist
- Recognition of urticarial vasculitis — a wheal fixed for more than a day, burning rather than itching, or leaving a bruise — and the biopsy threshold
- Angioedema: separating the histamine-mediated swelling that travels with urticaria from the bradykinin-mediated forms caused by ACE inhibitors or hereditary C1-inhibitor deficiency
- Practical advice for the heat- and sweat-triggered forms, which are genuinely limiting in this climate
- Written instructions on when to go to emergency care
Who it suits
- Someone whose wheals have been coming and going for weeks or months, who wants the condition brought under control and followed up — rather than something to end each attack as it arrives
- Someone who wheals where the skin is scratched, or under a waistband, a bra strap or a bag handle, or in the heat and sweat of the middle of the day. Those are the inducible forms, recognized from the history and from a simple test at the visit, not from allergy testing
- Someone who has been through wide allergy panels and long lists of forbidden foods and is no better, and who is now avoiding foods for a reason nobody can point to
- Someone pregnant or breastfeeding who has been told to stop everything and put up with it. The itch of pregnancy is a subject of its own, and which medicine can be used is a conversation with the doctor looking after your pregnancy — not silence
- Not you if what you want is the test that names the food. In chronic urticaria a cause outside the body is usually not found; the workup here is small and aimed at a few particular questions, and we would rather say so at the first visit than order you a panel that returns answers with nothing behind them. If the panel is what you want, this is not the room for it
When we advise delaying or not treating
- A cortisone injection, or another course of cortisone tablets, to end this attack. The skin quiets for a short time, then the rash returns as the drug wears off — often more stubbornly than before — so the next injection is asked for sooner, and the cycle keeps turning. A long-acting injection cannot be taken back out once it is given: its effect runs its course and its side effects run alongside it. In chronic urticaria this is not the treatment and it is not what is done here. One short course, decided by a doctor who has examined you, has its place in a severe sudden attack; being given an injection every time the rash comes back does not
- Raising your own antihistamine dose, or taking two products at once. Raising the dose above the standard one is a genuine step in chronic urticaria — but a supervised step, on a non-sedating antihistamine, with a review date. Taken on your own it usually means doubling a sedating one instead, or adding a product that already contains an antihistamine, which is exactly where cold and flu combinations catch people out
- Starting a sedating antihistamine in someone who drives at night, works shifts, is sitting exams, or is caring for a newborn — without saying plainly what it does. We would rather change the plan than hand it over quietly. What it does to alertness is in the list below
- A broad allergy panel, or a food panel, requested by name. In chronic spontaneous urticaria we decline to order it. It returns positive results that mean nothing on their own, and the long food restriction that follows takes a great deal from a household and gives nothing back. It is worse, not better, in pregnancy and in children, where eating less is not a neutral decision. A clear history tying one particular food to one particular attack shortly afterwards is a different matter, and that is asked about
- Swelling with no wheals at all in someone taking a blood-pressure tablet of the ACE-inhibitor group. That is a different mechanism, antihistamines do not touch it, and it can begin months or years after the tablet was started. The tablet is changed by the doctor who prescribed it — never stopped on your own — and the swelling is not managed here as though it were urticaria
- Swelling that keeps returning with no wheals at all, especially with a family history or with attacks of abdominal pain. Referred for complement and C1-inhibitor testing rather than treated as urticaria
- A spot that stays in one place for more than a day, burns rather than itches, or leaves a bruise behind. That is not ordinary urticaria; the next step is deciding whether a biopsy is needed, not a higher antihistamine dose
- Any elective treatment on the skin while the urticaria is active — laser, hair removal, peels, needling, and anything that heats, presses or rubs. In the inducible forms heat, pressure and friction are themselves the trigger, so a session can raise wheals across the whole treated area. It waits until the skin is quiet, and in pregnancy elective device work waits regardless
- Fat-freezing (cryolipolysis) in anyone with cold-induced urticaria. The treatment works by cooling, and cooling is her trigger; it is not offered
Possible effects
Stated in full, because the decision is not sound without them:
- Second-generation ("non-sedating") antihistamines are usually well tolerated, but "non-sedating" describes the group, not you. Drowsiness, headache, dry mouth and tiredness happen, and drowsiness becomes more likely as the dose goes up. Take the first dose of anything new on a day you are not driving and not handling anything that can hurt you
- First-generation sedating antihistamines — the old ones sold everywhere and usually taken at bedtime — impair driving and concentration into the following morning, while you feel wide awake. They add to anything else that sedates. They dry the mouth and eyes, blur vision, make passing urine harder in older men, and cause confusion and falls in older people. In a child, whether one is used at all is a doctor's decision, not a pharmacy's
- Raising the dose above the standard one is a supervised step with a review date, not a setting you leave switched on. Drowsiness rises with it, and if the wheals are no better on it then more of it is not the answer — the plan changes instead
- Systemic corticosteroids — tablets, or an injection into a muscle: the rash returning as they wear off, often more stubbornly than before; blood sugar rising, which matters a great deal if you have diabetes; blood pressure; disturbed sleep and changed mood; appetite and weight; a fuller face; more infections. Repeated over time: thinning bone, cataract and raised pressure in the eye, and suppression of the body's own cortisol production, which is why a steroid that has run for a while cannot simply be stopped one morning. A long-acting injection carries all of that and cannot be withdrawn once it has been given
- Omalizumab and the other second-line treatments are a referral, and a reviewed course rather than a single dose. The injections are given somewhere you can be observed afterwards, because a systemic allergic reaction, although uncommon, is possible. Symptoms may return when treatment stops, and that is said before it starts rather than after
- The broad allergy panel is itself a risk, not a neutral test: positives with no clinical meaning lead to months of avoiding foods, and in pregnancy and in childhood eating less carries consequences of its own
- Scratching opens the skin, and open skin becomes infected. On deeper skin tones the scratch marks and the thickened areas outlast the wheals themselves by months — the note below explains why. See skin infections if a scratch becomes sore, warm or crusted
- Undertreated urticaria has a cost that is not on the skin: broken sleep, difficulty at work and in study, and low mood. It is stated because it is an argument for treating steadily rather than in bursts, not a reason to accept it
- What ordinary urticaria does not do: it does not scar, and a wheal that has gone leaves nothing behind. A mark that stays where a wheal was is not an expected after-effect — it is a finding, and it is looked at
A note on darker skin
The medicine does not change with skin tone: urticaria is diagnosed and treated the same way at every skin type, and nothing in the tablet differs. What changes is what the eye can see. A wheal on deeper skin does not announce itself as red; on Fitzpatrick IV-VI it usually reads as a raised area that is skin-colored, slightly darker, or violaceous, and what you see is the swelling and the shape rather than any color — which is why urticaria on darker skin is routinely judged milder than it is, by patients and by clinicians reading a photograph. Two practical consequences follow. Photograph a flare in daylight and from an angle, not straight on under a ceiling light: raised skin shows in side light and vanishes in flat light, and the photograph is often the only evidence, because the day the appointment falls is usually a quiet day. And the tests done in the room follow the same rule — when a line is drawn on the skin to look for dermographism, what is read on deeper skin is the raised weal you can feel and see in relief, not a red line. The caution is not about the wheals at all; it is about the scratching. Ordinary urticaria leaves nothing behind, but scratching does, and on deeper skin the dark lines, the darkened patches and the thickened areas left by months of it outlast the rash by a long way and become the thing that distresses you most. That is the real argument for treating the itch steadily rather than in bursts: controlling it is also how the pigment is protected. Those marks fade as the itch fades, slowly and on their own; they are not treated with a lightening cream, and above all not with an unlabeled mixed cream, which thins the skin and leaves you worse off. And no laser, peel or needling goes over skin that is actively being scratched — post-inflammatory darkening is the likely result.
Afterwards
- Take it every day for the period agreed, not only on the days the rash appears. Taking it regularly is how an antihistamine holds urticaria down, and taking it only when wheals arrive is the commonest reason someone says the medicine did not work
- Make one observation and bring the answer with you: draw a ring around a single wheal with a pen, and look at that ring some hours later. If that wheal has gone and others have appeared elsewhere, that is ordinary urticaria. If it is still sitting inside the ring the next day, or it burns rather than itches, or it leaves a bruise, tell us — that changes the diagnosis and it changes what happens next
- Report any new medicine started anywhere, for anything — painkillers and antibiotics before all others, and any blood-pressure tablet
- Tell us if you become pregnant, are planning to, or are breastfeeding — and tell us at the time, not at the next visit. What you take changes that day, and a new itch in pregnancy is not assumed to be urticaria
- Tell us about any cortisone given to you for this rash anywhere — tablets or an injection. And if you are already on a course that has run for a while, do not stop it on your own; it is reduced under supervision
- Report drowsiness that has reached into your day: sleeping in the afternoon, foggy at work or in class, or feeling unsafe behind the wheel. That is a reason to change what you are on, not something to push through
- Report a scratch that has broken the skin and is now sore, warm, weeping or crusted — that is an infection and is treated as one
- Come back while it is quiet, too. Stepping treatment down is done deliberately and gradually; stopping it the day the skin clears is what brings the wheals straight back and convinces people the condition never improved at all
Honestly
Most chronic urticaria has no findable external cause, and broad allergy panels usually mislead and push patients into food restriction that does not help.
Common questions
I had a cortisone injection once and it cleared in two days. Why not repeat it every time?
Because the problem is not the two days, it is coming off it. The injection suppresses the inflammation for a while; when it wears off the rash returns, often more stubbornly than before, so the next injection is asked for sooner than the last. That turns the condition into a cycle of injections rather than a treatment. And a long-acting injection cannot be taken back out once it is given: it runs its course and its effects run with it — blood sugar, blood pressure, sleep, mood, weight, infections, and with repetition the bone, the eyes, and suppression of the body's own cortisol production. One short course decided by a doctor who has examined you in a severe sudden attack is one thing; an injection every month is another thing entirely. And if you are genuinely on cortisone already, do not stop it by yourself — tell us, and it is reduced gradually.
I want the allergy test that shows me which food is doing this.
We understand the wish completely, and the honest answer is that the broad panel does not give it to you. In chronic urticaria a cause outside the body is usually not found, and wide testing returns positives for foods you have been eating for years without trouble, which then get banned from the house for nothing. What does help is a precise history: one food or one medicine, shortly before the attack, happening again. That we ask about and follow. The tests we do order are few and aimed — thyroid autoimmunity among them. NSAIDs and antibiotics we ask about directly, because they are more often involved than people expect.
I'm pregnant and covered in an itchy rash. Do I take something or put up with it?
Do not put up with it, and do not buy anything yourself. First: not every itch in pregnancy is urticaria. There is a polymorphic eruption that usually begins in the stretch marks of the abdomen and spares the navel, and its spots stay in place rather than fading within the day the way wheals do; and there is pemphigoid gestationis, which often begins around the navel and can go on to blister, and which needs a specialist diagnosis and follow-up with the doctor caring for your pregnancy. The one that matters most for the baby has no rash at all: intense itching with nothing to see, commonly on the palms and soles and worse at night, with only the marks of scratching on the skin — that is reported the same day to whoever is looking after your pregnancy, and blood tests of the liver and the bile acids are asked for. As for medicine, it is chosen with the doctor caring for your pregnancy; not every antihistamine on the shelf is the one chosen, and raising the dose is a different decision in pregnancy. While breastfeeding we avoid the sedating ones: they pass into the milk and can make a baby drowsy and feed poorly, and they slow you down when you are the one caring for the baby.
The tablet has stopped working. Should I take two?
Raising the dose is a recognized step in chronic urticaria, but a supervised one: on a particular non-sedating antihistamine, by decision, with a review date at which it is judged whether it helped. Three things worry us when it is done alone: that it means doubling a sedating one, which is not the same step and doubles what it does to your alertness; that you already have a cold or flu product containing an antihistamine, so you are taking two while counting one; and that the raised dose then continues for months without review even though it did not help. Tell us before you raise it — and if raising it does not work, the plan changes rather than climbing further.
I take the sleepy one at night and drive in the morning. Is that a problem?
Yes, and it is one of the things we see most. First-generation sedating antihistamines carry their effect on alertness, concentration and reaction time into the next morning, and the difficulty is that you feel wide awake when you are not — the feeling does not measure this. Anything else that sedates adds to it. That is why we ask at the start about driving, work, study and looking after children, and build the choice around the answers. If what you have in your hand now is a sedating one and you drive, tell us and we will change it.
My whole body is covered and the itch is unbearable. Should I go to emergency?
Judge by the list, not by the area. An itchy raised rash over the whole body, with no swelling of the lips, tongue or throat, no change in your voice, no difficulty breathing or swallowing, no faintness, and no vomiting or abdominal cramping, does not threaten your airway however widespread it is and however alarming it looks. It is genuinely miserable, and it is not an emergency: take what you have been given and message us in clinic hours. If any one item on that list does appear, then it is emergency care immediately, without waiting for any tablet to work. The full list is in the box higher up this page.