SOS Allergo · I understand & manage
Chronic spontaneous urticaria
Understanding wheals, swelling and why an ‘allergen’ is not always found
In this sheet
3 essential points
Chronic urticaria is not a ‘chronic allergy’
Wheals that recur for more than 6 weeks do not mean that a food, pollen or dust mite necessarily sustains the disease. CSU is an inflammatory mast-cell disease.
Routine food exclusions are often unnecessary
In CSU, endlessly searching for a hidden food or removing several foods often leads to unnecessary restrictions. Assessment should remain guided by the clinical history.
There is a stepwise treatment strategy
Second-generation H1 antihistamines are first-line treatment. If control remains inadequate, the doctor may adapt treatment and then discuss a biologic, particularly omalizumab.
What does an urticarial wheal look like?
- a raised wheal, often pink, red or skin-coloured;
- very itchy;
- it may change shape or location;
- in the same place, it usually disappears within 24 hours, even if other wheals appear elsewhere.
Deeper angioedema may accompany the wheals, especially on the lips or eyelids, and may last longer.
Why ‘chronic’ and ‘spontaneous’?
- Term
- Chronic
- What it means
- Flares recur for more than 6 weeks. This does not mean that urticaria will last for life.
- Term
- Spontaneous
- What it means
- Lesions appear without an obligatory, reproducible physical trigger. This means neither ‘without a mechanism’ nor ‘psychological’.
| Term | What it means |
|---|---|
| Chronic | Flares recur for more than 6 weeks. This does not mean that urticaria will last for life. |
| Spontaneous | Lesions appear without an obligatory, reproducible physical trigger. This means neither ‘without a mechanism’ nor ‘psychological’. |
CSU and inducible urticaria can coexist in the same person.
See also: ‘Inducible urticaria’.
Is it an allergy?
In CSU, food allergy and allergy to pollen, dust mites or animals are generally not the cause. Extensive allergy testing without a suggestive history therefore does not explain the disease in most cases.
Why do some things seem to worsen flares?
A factor may temporarily increase symptoms without being the underlying cause of CSU. In some patients, NSAIDs such as ibuprofen or aspirin, alcohol, heat, some infections, fatigue or stress may coincide with worsening.
Stress does not mean an imaginary illness: it may modulate flares, but CSU remains an inflammatory disease.
See also: ‘Hypersensitivity to NSAIDs and aspirin’.
Which tests are needed?
Diagnosis is mainly clinical. The history, appearance and duration of lesions, angioedema, medicines and unusual signs guide assessment. Guidelines favour limited, targeted investigations rather than a long battery of tests.
When should another condition be considered?
Tell your doctor if a lesion stays in the same place for more than 24 hours, is mainly painful, leaves bruising or persistent discoloration, or occurs with fever, joint pain or unusual systemic symptoms. Repeated swelling without any wheals also deserves specific assessment.
How is CSU treated?
The aim is to achieve complete or near-complete control of wheals, itching and swelling while the disease is active. An allergen does not need to be identified for effective treatment.
- Step
- 1. First line
- Principle
- A second-generation H1 antihistamine according to the medical plan.
- Step
- 2. Inadequate control
- Principle
- The doctor may increase the dose above the usual dose, up to four times the standard dose in some guidelines.
- Step
- 3. Still inadequate
- Principle
- A biologic, particularly omalizumab, may be considered when indicated.
- Step
- 4. Refractory forms
- Principle
- Other specialist treatments may be considered with medical monitoring.
| Step | Principle |
|---|---|
| 1. First line | A second-generation H1 antihistamine according to the medical plan. |
| 2. Inadequate control | The doctor may increase the dose above the usual dose, up to four times the standard dose in some guidelines. |
| 3. Still inadequate | A biologic, particularly omalizumab, may be considered when indicated. |
| 4. Refractory forms | Other specialist treatments may be considered with medical monitoring. |
Never change the dose or frequency of prescribed treatment yourself.
Antihistamines: key points
Second-generation H1 antihistamines are first-line treatment. In CSU, they are often more effective when taken regularly according to the prescribed plan rather than only after a major flare appears.
See ‘Using H1 antihistamines correctly’.
Corticosteroids are not maintenance treatment
What if antihistamines are not enough?
Omalizumab is a standard biologic treatment for CSU that remains inadequately controlled despite appropriate antihistamine treatment. Choice, dosing interval and duration are determined by the medical team.
See ‘Understanding and monitoring biologic therapy’.
Monitoring the condition
Should autoimmune disease be investigated?
Autoimmune mechanisms occur in some CSU profiles, and some associations, particularly with thyroid disease, are better recognised. This does not mean that every autoimmune disease should be sought in every patient: additional tests depend on the context.
How do I know whether urticaria is controlled?
Follow-up considers wheal and swelling frequency, itching, sleep and everyday impact. Validated tools such as the Urticaria Control Test (UCT) may be used by teams to measure control. This sheet neither reproduces nor calculates that score.
Associated angioedema: when is it an emergency?
Swelling of the lips or eyelids may be part of CSU. In contrast, acute swelling of the tongue or throat with breathing difficulty, feeling faint or a severe presentation requires emergency care.
Emergency
If you have a personal emergency plan, follow it. For breathing difficulty, severe faintness or rapid worsening, call 15 or 112.
Repeated swelling without urticaria must be distinguished from other forms of angioedema.
See ‘Angioedema without urticaria’.
Everyday life
Photographing wheals is very useful
Lesions may have disappeared by the appointment. If possible, take a clear photograph and note the date, how long the wheal lasted in the same place, whether swelling occurred and which treatment was taken.
Quality of life: describe what the disease stops you doing
CSU may disrupt sleep, work, school, physical activity, social life and body image. This impact is part of the disease and should be discussed even if lesions are not visible at the appointment.
Is it contagious?
No. Chronic spontaneous urticaria is not contagious and is not an accumulation of ‘toxins’ that must leave through the skin.
Does it eventually go away?
Often yes, but duration varies greatly. CSU may last months or several years and then go into remission. Treatment controls symptoms during the active period, with regular reassessment of whether it is still needed.
Common misconceptions
- Misconception
- ‘I must be eating something that makes me allergic.’
- SOS Allergo guidance
- In CSU, food allergy is generally not the cause.
- Misconception
- ‘Every possible test is needed.’
- SOS Allergo guidance
- No. Assessment is mainly clinical and targeted.
- Misconception
- ‘If no cause is found, nothing can be done.’
- SOS Allergo guidance
- False. Treatment aims to control the disease.
- Misconception
- ‘An urticarial wheal stays in the same place for several days.’
- SOS Allergo guidance
- That is not typical and should be discussed with a doctor.
- Misconception
- ‘Cortisone is the maintenance treatment.’
- SOS Allergo guidance
- No. Systemic corticosteroids should not be used long term for CSU.
- Misconception
- ‘It is stress, so it is psychological.’
- SOS Allergo guidance
- No. Stress may modulate flares; CSU remains an inflammatory mast-cell disease.
| Misconception | SOS Allergo guidance |
|---|---|
| ‘I must be eating something that makes me allergic.’ | In CSU, food allergy is generally not the cause. |
| ‘Every possible test is needed.’ | No. Assessment is mainly clinical and targeted. |
| ‘If no cause is found, nothing can be done.’ | False. Treatment aims to control the disease. |
| ‘An urticarial wheal stays in the same place for several days.’ | That is not typical and should be discussed with a doctor. |
| ‘Cortisone is the maintenance treatment.’ | No. Systemic corticosteroids should not be used long term for CSU. |
| ‘It is stress, so it is psychological.’ | No. Stress may modulate flares; CSU remains an inflammatory mast-cell disease. |
Key points
- CSU means wheals, angioedema or both recurring for more than 6 weeks.
- Food or environmental allergy is generally not the cause.
- Assessment should remain targeted: multiple tests and exclusions are often unnecessary.
- Second-generation antihistamines are first-line treatment; more advanced treatments are available if needed.
- The aim is disease control and preservation of quality of life.
Preparing for the appointment
If possible, bring dated photographs and note how long a wheal lasts in one place, whether angioedema occurs, medicines taken, especially NSAIDs, factors that appear to worsen flares and the actual effect of treatment. This is more useful than a list of foods removed at random.
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Main references
- Zuberbier T, et al. The international EAACI/GA²LEN/EuroGuiDerm/APAAACI guideline for urticaria. Allergy. 2022;77:734-766. DOI: 10.1111/all.15090. PMID: 34536239.
- Kolkhir P, Bonnekoh H, Metz M, Maurer M. Chronic Spontaneous Urticaria: A Review. JAMA. 2024;332:1464-1477. DOI: 10.1001/jama.2024.15568. PMID: 39325444.
- Friedman A, Kwatra SG, Yosipovitch G. A Practical Approach to Diagnosing and Managing Chronic Spontaneous Urticaria. Dermatol Ther (Heidelb). 2024;14:1371-1387. DOI: 10.1007/s13555-024-01173-5. PMID: 38758422.
- Metz M, et al. The Diagnostic Workup in Chronic Spontaneous Urticaria - What to Test and Why. J Allergy Clin Immunol Pract. 2021;9:2274-2283. DOI: 10.1016/j.jaip.2021.03.049. PMID: 33857657.
- Lang DM. Management of chronic urticaria: Treatment options when omalizumab fails. Allergy Asthma Proc. 2025;46:455-461. DOI: 10.2500/aap.2025.46.250072. PMID: 41152678.
- Sánchez J, et al. Chronic spontaneous urticaria remission definition and therapy stepping down: World Allergy Organization position paper. J Allergy Clin Immunol. 2025;155:1050-1056.e2. DOI: 10.1016/j.jaci.2024.11.039. PMID: 39732405.
General information: this sheet does not make a diagnosis, replace your care plan or justify changing treatment yourself. In an emergency, call 15 or 112.
Scientific review: September 2026 · sosallergo.fr