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Urticaria
Weals that come and go: how long each single lesion lasts is what matters.
In dermatology, time is a clinical sign, and urticaria is the clearest example. Patients arrive saying "I have had these patches for a week," but the question that guides the diagnosis is a different one: has each individual patch stayed in the same place for a week, or does it disappear and reappear elsewhere?
The typical urticarial weal is a raised, oedematous lesion, often intensely itchy, that appears quickly and resolves just as quickly — usually within twenty-four hours. In the meantime, however, others may appear at different sites, making an eruption that is in fact continually renewing itself look continuous. This is where the gap arises between what the patient perceives and what the physician is looking for.
The distinction is not academic. A single lesion that stays fixed in the same place beyond twenty-four hours, particularly if it is painful rather than itchy or leaves a mark when it fades, is an element that leads to considering alternative diagnoses. Recognising this difference changes the pathway.
One practical piece of advice worth more than many descriptions: photograph the eruption while it is there. The lesions are fleeting by definition, and they have often already gone by the time of the visit. A photo taken at the right moment, with the time, can tell the dermatologist what the examination itself can no longer show.
Time the weal, not the eruption
The question to bring to the visit is not "how long have I had urticaria" but "how long does each single lesion last". Mark where a weal appears and check that same spot a few hours later: if it has gone within a day, the behaviour is typical. If it stays fixed, that is information the dermatologist wants — and that no test can recover afterwards.
How it shows
- Raised weals, pink or pale, with well-defined edges
- Itching, often intense
- The individual lesion appears and fades, usually within 24 hours
- New lesions appear at different sites as earlier ones resolve
- The skin returns to normal where the weal has gone
- In some cases deeper swelling of lips, eyelids or hands
How we proceed
- 1Dermatological visit: duration of the individual lesion, not just of the eruption
- 2Skin examination and assessment of lesions present at the time
- 3Review of possible triggers and current medication
- 4Distinction between common forms and pictures requiring further investigation
- 5Definition of management and, where needed, scheduled follow-up
Available treatments
- Dermatology visit
- Diagnostic assessment
- Assessment of triggers
- Management of the active phase
- Follow-up over time
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Frequently asked questions
I have had it for weeks: why do you ask how long a single weal lasts?+
Because they are two different things. Urticaria as a whole can last a long time precisely because the lesions keep renewing: what looks like the same weal is often a succession of different ones. The duration of the individual lesion, however, is data that guides the diagnosis. In the common form it resolves within twenty-four hours.
When should I be concerned?+
One element to report is a lesion that stays fixed in the same place beyond twenty-four hours, especially if it is more painful than itchy or leaves a mark when it fades. Deep swelling of the lips, eyelids, tongue or throat should also be reported, and requires urgent assessment rather than a scheduled appointment.
Do I need allergy tests?+
Not always, and not as an automatic first step. Many cases of urticaria have no identifiable allergic cause, and starting with tests without clinical suspicion often produces results that are hard to interpret. Whether and which investigations to perform is decided at the visit, based on the history: how long it has lasted, how it behaves, what seems to trigger it.
Should I come while the lesions are present?+
That would be ideal, but the timing rarely matches: the lesions are fleeting and often disappear before the appointment. The practical solution is therefore to photograph them while they are there, ideally with the time, and bring the photos to the visit. They are worth as much as examining skin that has meanwhile returned to normal.
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