The 24-hour rule
An urticarial weal is fleeting: it appears, itches, and disappears completely within 24 hours, leaving no mark or scar — even though others appear elsewhere meanwhile. That behaviour is the hallmark of the disease.
If a lesion lasts more than a day in the same place, hurts or burns more than it itches, or leaves a mark when it fades, then it is probably not ordinary urticaria and needs different investigation, possibly a biopsy. Say so in consultation: it changes the diagnosis.
Acute or chronic — and why it matters so much
Acute urticaria (under 6 weeks): there is often an identifiable trigger — a viral infection, a drug, sometimes a food. It usually resolves on its own.
Chronic urticaria (over 6 weeks): here lies the most expensive misunderstanding in this disease. In the great majority of cases NO external cause is found, and in particular it is not food allergy. The immune system is releasing histamine by itself, often through an autoimmune mechanism.
The practical consequence matters: elimination diets and blanket allergy panels “just in case” are, in chronic urticaria, an enormous source of frustration, expense and needless dietary restriction — and they rarely find anything. The right treatment is not to hunt for a culprit: it is to control the histamine.
When it is an emergency
Urticaria itself is not dangerous, however maddening it is. But some signs demand immediate attention, because they can indicate a severe allergic reaction (anaphylaxis):
- Swelling of lips, tongue, eyelids or throat (angioedema).
- Difficulty breathing, swallowing or speaking, or a feeling of tightness in the throat.
- Dizziness, fainting, vomiting or severe abdominal pain alongside the hives.
- In any of these: emergency department, now. Do not wait for a consultation.
How it is treated
Prescribed and supervised in the dermatology consultation. No drug names or doses here:
- Antihistamines, regularly and on the prescribed schedule — not “only when the hives appear”. Taking them on demand is the commonest error: nothing gets controlled that way.
- Therapeutic escalation when the standard dose is not enough. Later lines of treatment exist, and they work.
- Identifying physical triggers that genuinely are real: pressure, cold, heat, exercise, water, vibration. Some chronic urticarias are inducible, and that can be recognised.
- Targeted investigation, not a blind panel. Causes are sought when the history suggests one.
- Patience: chronic urticaria remits on its own in many patients over time. Meanwhile, the goal is that you live normally, without itch.
Who treats it here
Diagnosis and treatment of urticaria belong to the clinic’s dermatology consultation — the same one with which Dr. Francisco Arellano Ocampo founded the house in 1971. Dr. Arístides Arellano is a plastic surgeon, not a dermatologist: his contribution here is surgical and reconstructive, and the disease itself is managed in the consultation. Book at dermatology consultation.
Dr. Arístides Arellano is a plastic surgeon holding a specialty licence: he practises under a Mexican medical licence (D.G.P. 1125959) and a specialty licence in Plastic & Reconstructive Surgery (0002008), both issued by the Directorate General of Professions (DGP), which reissued his certificate of professional standing in 2025. His career began before Mexico’s present-day specialty-board system existed: he belongs to the founding generation of plastic surgery in Puebla, the second generation of a surgical tradition started in 1971 by Dr. Francisco Arellano Ocampo. Trust is verified, not promised: both licences are public and anyone can look them up in the DGP’s National Registry of Professionals.
Risks and expectations
Every medical treatment —topicals, peels and energy-based devices included— carries risk and requires a prior assessment. In darker skin (Fitzpatrick IV–VI, the most common phototypes in Mexico) a poorly indicated procedure can darken the patch instead of lightening it. Results may vary according to each patient, their phototype and their individual triggers.
Trust is verified, not promised. All 210 scanned documents —degree, licences, diplomas, publications and certificates, from 1977 to 2025— are open in Dr. Arístides Arellano’s credential archive, alongside an explanation of the difference between a specialty licence and a board certification.
Control plan
- DiagnosisDermatology consultation. The 24-hour rule defines the picture.
- Acute (<6 wks)Often a trigger. Usually resolves on its own.
- Chronic (>6 wks)In most cases NO external cause. It is not food allergy.
- TreatmentRegular antihistamine on the prescribed schedule, not on demand.
- EmergencyLip/tongue/throat swelling or breathing difficulty: emergency department NOW.
- PrognosisRemits on its own in many patients over time.
Frequently asked questions
Is chronic urticaria an allergy to something I eat?
Almost never. When urticaria lasts more than six weeks, in the great majority of cases no external cause is found, and in particular it is not food allergy: the immune system releases histamine by itself, often through an autoimmune mechanism. Elimination diets and blanket allergy panels “just in case” are an enormous source of frustration and needless restriction, and they rarely find anything.
How do I know it is urticaria and not something else?
By the 24-hour rule: the weal appears, itches, and disappears completely within a day leaving no mark, even though others appear elsewhere. If a lesion lasts more than 24 hours in the same place, hurts or burns rather than itches, or leaves a mark when it fades, it is probably not ordinary urticaria and needs different investigation, possibly a biopsy.
When must I go to the emergency department?
If there is swelling of the lips, tongue, eyelids or throat; if you have difficulty breathing, swallowing or speaking; or if there is dizziness, fainting, vomiting or severe abdominal pain alongside the hives. That can be a severe allergic reaction and it does not wait for a consultation: emergency department, immediately.
Are antihistamines only taken when the hives appear?
No, and that is the commonest error. In chronic urticaria they are taken regularly, on the prescribed schedule, to keep histamine controlled. Taking them on demand lets the disease stay ahead of you. If the standard dose is not enough, later lines of treatment exist and work, and they are prescribed in consultation.
Does chronic urticaria go away?
In many patients it remits on its own over time, although it can take months or years. Meanwhile, the goal of treatment is that you live normally and without itch. It is not a dangerous disease, but it can be highly disabling, and controlling it well changes daily life.
Every case is different. Discuss yours in a personal consultation.
Book a consultation on WhatsAppEvery figure published on this site is approximate and is not a quote. Any procedure or treatment first requires a private assessment consultation with Dr. Arístides Arellano —$800 MXN, charged separately— and it is at that consultation that the definitive cost of your case is determined.
Educational content; it does not replace a medical consultation. Results may vary from person to person.