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Understanding and monitoring biologic treatment
What is it for, which conditions can it treat, how is it chosen and what monitoring is needed?
A biologic is a targeted treatment, usually a monoclonal antibody, that blocks a specific step in inflammation. It is offered after confirming the condition, assessing its severity and checking that usual treatments have been optimised.
In this sheet
3 essential points
A biologic targets a specific mechanism
Depending on the condition, treatments may target IgE, the IL-4/IL-13 pathways, IL-5/eosinophils or TSLP. Two patients with the same condition may therefore receive different treatments.
It is not prescribed on a biomarker alone
Eosinophils, IgE or FeNO may help in some conditions, but the decision also considers symptoms, flares, treatments already tried, comorbidities and authorised indications.
Biologic treatment must be reassessed
The team checks whether it actually reduces symptoms, exacerbations, corticosteroid use and the effect on daily life. An ineffective treatment should not be continued automatically.
Indications and choice
Which conditions can be treated?
Examples as at 11 September 2026. Indications, age limits, access conditions and reimbursement may change.
- Condition
- Severe asthma
- Examples of biologic therapies
- Omalizumab, mepolizumab, benralizumab, dupilumab or tezepelumab depending on the profile.
- Condition
- Chronic spontaneous urticaria
- Examples of biologic therapies
- Omalizumab; dupilumab in some profiles according to its European indication.
- Condition
- Moderate-to-severe atopic dermatitis
- Examples of biologic therapies
- Dupilumab and other targeted dermatology treatments depending on age and circumstances.
- Condition
- Severe chronic rhinosinusitis with nasal polyps
- Examples of biologic therapies
- Dupilumab, omalizumab, mepolizumab or tezepelumab according to the indication.
- Condition
- Eosinophilic oesophagitis
- Examples of biologic therapies
- Dupilumab in some situations.
- Condition
- EGPA / hypereosinophilic syndrome
- Examples of biologic therapies
- Some biologics targeting the eosinophil pathway in specialist care.
| Condition | Examples of biologic therapies |
|---|---|
| Severe asthma | Omalizumab, mepolizumab, benralizumab, dupilumab or tezepelumab depending on the profile. |
| Chronic spontaneous urticaria | Omalizumab; dupilumab in some profiles according to its European indication. |
| Moderate-to-severe atopic dermatitis | Dupilumab and other targeted dermatology treatments depending on age and circumstances. |
| Severe chronic rhinosinusitis with nasal polyps | Dupilumab, omalizumab, mepolizumab or tezepelumab according to the indication. |
| Eosinophilic oesophagitis | Dupilumab in some situations. |
| EGPA / hypereosinophilic syndrome | Some biologics targeting the eosinophil pathway in specialist care. |
When is a biologic considered?
- confirm the diagnosis and severity of the condition;
- check that usual treatments have been used correctly and sufficiently optimised;
- identify aggravating factors and comorbidities;
- identify the inflammatory profile and relevant biomarkers when useful;
- choose a medicine with an indication suited to the patient and condition.
Example: severe asthma
Before starting a biologic, the team checks inhaled treatment, inhaler technique, adherence, exacerbations, comorbidities and the inflammatory profile. A biologic is an add-on treatment, not an automatic replacement for inhalers.
How is the right biologic chosen?
The choice depends on the condition, age, exacerbations or flares, corticosteroid requirements, useful biomarkers, other associated conditions and authorisation requirements. A medicine that treats several conditions may be helpful, but is not automatically best for everyone.
Administration and follow-up
How is it administered?
Most biologics used in allergy care are injected under the skin. Depending on the product, injections may be given by a professional or, after training and a medical decision, by the patient or a caregiver using a pre-filled syringe or pen.
A biologic is not…
- How they differ
- … chemotherapy. It targets a specific inflammatory pathway.
- Key points
- … desensitisation. It does not work like allergen immunotherapy.
- How they differ
- … an emergency treatment.
- Key points
- … a reason to stop other maintenance treatments on your own.
| How they differ | Key points |
|---|---|
| … chemotherapy. It targets a specific inflammatory pathway. | … desensitisation. It does not work like allergen immunotherapy. |
| … an emergency treatment. | … a reason to stop other maintenance treatments on your own. |
What checks are needed before starting?
There is no single universal assessment for every biologic. The team primarily checks the diagnosis, severity, treatments already tried, comorbidities, indication criteria and, depending on the condition, certain tests or biomarkers.
- Condition
- Severe asthma
- What follow-up mainly assesses
- Exacerbations, corticosteroids, clinical control and lung function; eosinophils, IgE or FeNO depending on the biologic considered.
- Condition
- Chronic urticaria
- What follow-up mainly assesses
- Wheals, angioedema, itching and level of control.
- Condition
- Atopic dermatitis
- What follow-up mainly assesses
- Lesions, itching, sleep, infections and quality of life.
- Condition
- Nasal polyps
- What follow-up mainly assesses
- Nasal obstruction, sense of smell, corticosteroids or surgery.
- Condition
- Eosinophilic oesophagitis
- What follow-up mainly assesses
- Symptoms as well as endoscopic and histological assessment according to the specialist plan.
| Condition | What follow-up mainly assesses |
|---|---|
| Severe asthma | Exacerbations, corticosteroids, clinical control and lung function; eosinophils, IgE or FeNO depending on the biologic considered. |
| Chronic urticaria | Wheals, angioedema, itching and level of control. |
| Atopic dermatitis | Lesions, itching, sleep, infections and quality of life. |
| Nasal polyps | Nasal obstruction, sense of smell, corticosteroids or surgery. |
| Eosinophilic oesophagitis | Symptoms as well as endoscopic and histological assessment according to the specialist plan. |
Effects and precautions
Adverse effects: what should be monitored?
They vary between medicines: injection-site reactions, headaches or general symptoms with some products, and rare allergic reactions. Some biologics also have particular effects, such as eye symptoms or changes in eosinophil counts. Read your product leaflet and report any unusual symptom.
Does it ‘weaken the immune system’?
A targeted biologic does not work like a conventional general immunosuppressant: it blocks a specific immune pathway. This does not mean it has no effect on the immune system. Infection risks and precautions vary according to the target and product.
Vaccinations, pregnancy and other treatments
- Vaccinations: ask whether any vaccinations should be updated and whether your product requires particular precautions.
- Pregnancy / planning a pregnancy: do not stop a biologic abruptly; contact the specialist to reassess benefits and risks.
- Other treatments: do not stop them simply because the biologic is working better. Any reduction should be agreed with the team.
How long does treatment continue?
There is no universal duration. Continuation depends on effectiveness, tolerability, disease control and relapse risk. Some biologics are long-term treatments, but the need to continue them must be reassessed regularly.
Who can prescribe it in France?
Since 2024, the requirement for the first prescription to be issued in hospital has been removed for many subcutaneous biologics. This does not make them freely available: prescription, initiation and reimbursement rules remain specific to each medicine.
Common misconceptions
- Misconception
- ‘A biologic is chemotherapy.’
- SOS Allergo guidance
- No. It targets a specific inflammatory pathway.
- Misconception
- ‘My eosinophils are high, so I need one.’
- SOS Allergo guidance
- No. A biomarker alone is not enough.
- Misconception
- ‘Once I start the biologic, I stop my other treatments.’
- SOS Allergo guidance
- No, unless instructed by the medical team.
- Misconception
- ‘If I feel better, I can space out the injections myself.’
- SOS Allergo guidance
- No.
- Misconception
- ‘All biologics require the same blood tests.’
- SOS Allergo guidance
- False. Monitoring depends on the product and condition.
- Misconception
- ‘Biologic treatment means treatment for life.’
- SOS Allergo guidance
- Not necessarily; it must be reassessed regularly.
| Misconception | SOS Allergo guidance |
|---|---|
| ‘A biologic is chemotherapy.’ | No. It targets a specific inflammatory pathway. |
| ‘My eosinophils are high, so I need one.’ | No. A biomarker alone is not enough. |
| ‘Once I start the biologic, I stop my other treatments.’ | No, unless instructed by the medical team. |
| ‘If I feel better, I can space out the injections myself.’ | No. |
| ‘All biologics require the same blood tests.’ | False. Monitoring depends on the product and condition. |
| ‘Biologic treatment means treatment for life.’ | Not necessarily; it must be reassessed regularly. |
Before my appointment / during follow-up
- condition being treated
- current treatments
- flares/exacerbations
- corticosteroids received
- hospital admissions
- other inflammatory/allergic conditions
- vaccinations
- pregnancy plans
- treatments already tried
- injection dates
- missed doses
- adverse effects
- changes in quality of life
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References and resources
- Haute Autorité de Santé. Bon usage des biothérapies dans l'asthme sévère : Dupixent, Fasenra, Nucala, Tezspire et Xolair. Ressources HAS.
- European Medicines Agency (EMA). EPAR : Xolair, Dupixent, Nucala, Fasenra et Tezspire. Indications européennes consultées en septembre 2026.
- EMA. Dupixent : indications incluant notamment dermatite atopique, asthme de type 2, polypose, œsophagite à éosinophiles et urticaire chronique spontanée selon les populations autorisées. Mise à jour 2026.
- EMA. Nucala : asthme éosinophilique sévère, polypose, EGPA et syndrome hyperéosinophilique selon les populations autorisées. Mise à jour 2026.
- Haute Autorité de Santé. Évolution 2024 des conditions de prescription des biothérapies sous-cutanées dans les maladies inflammatoires chroniques.
- Base de Données Publique des Médicaments. Conditions françaises de prescription et de délivrance ; mise à jour consultée du 31 août 2026.
Scientific review: September 2026 · sosallergo.fr