SOS Allergo · I understand & manage
Itching: why does skin itch?
With or without visible skin lesions: finding the cause without unnecessary tests
Pruritus is the sensation that makes you want to scratch. It may accompany a common skin condition, be promoted by a medicine or a particular environment or, less commonly, reveal a systemic disease. The investigation starts with one essential question: were lesions present before the itching began, or did they appear because of repeated scratching?
In this sheet
3 essential points
Lesions before itching point first to a skin condition
Possible causes include eczema, urticaria, scabies, contact dermatitis, bites, fungal infection or psoriasis.
If the skin looked normal at first, the investigation is different
Dry skin, medicines, iron deficiency, liver, kidney or thyroid disease, metabolic disorders or a neurological cause may be considered depending on the context.
Scratch marks are not necessarily the cause
Excoriations, crusts, thickening or nodules may develop after weeks of scratching. Try to remember what the skin looked like initially.
First question: were there lesions before the itching began?
- The skin was already abnormal
- Eczema / atopic dermatitis · urticaria · contact dermatitis · scabies, bites, fungal infection · psoriasis or certain blistering diseases.
- The skin looked normal
- Sometimes subtle dry skin · medicine · liver/cholestasis or kidney disease · iron deficiency · thyroid disease, diabetes or another metabolic disorder · neurological cause; less commonly another systemic disease.
| Initial appearance | Possible explanations |
|---|---|
| The skin was already abnormal | Eczema / atopic dermatitis · urticaria · contact dermatitis · scabies, bites, fungal infection · psoriasis or certain blistering diseases. |
| The skin looked normal | Sometimes subtle dry skin · medicine · liver/cholestasis or kidney disease · iron deficiency · thyroid disease, diabetes or another metabolic disorder · neurological cause; less commonly another systemic disease. |
Pruritus with lesions: some clues
- Dry, red or oozing patches may suggest eczema or contact dermatitis.
- Raised wheals that usually disappear from the same place within 24 hours suggest urticaria.
- Small spots with mainly night-time itching, especially when several close contacts also itch, suggest scabies.
The history: the key diagnostic tool
- Since when?
- Distinguish recent itching from chronic itching lasting at least 6 weeks.
- Where?
- Localised or generalised; hands, legs, scalp, folds, genital area, palms or soles.
- When?
- Evening, night, attacks or constant; intense night-time itching may suggest scabies.
- What does it feel like?
- Itching, burning, tingling or electric-shock sensations may suggest neuropathic itch.
| Question | Why it helps |
|---|---|
| Since when? | Distinguish recent itching from chronic itching lasting at least 6 weeks. |
| Where? | Localised or generalised; hands, legs, scalp, folds, genital area, palms or soles. |
| When? | Evening, night, attacks or constant; intense night-time itching may suggest scabies. |
| What does it feel like? | Itching, burning, tingling or electric-shock sensations may suggest neuropathic itch. |
Animals: why does the doctor ask?
Mention dogs, cats, rodents, rabbits, birds, farm animals or the recent arrival of an animal. Depending on the lesions, this may suggest flea or other arthropod bites, some fungal infections transmitted by animals, or other exposures.
Recent travel: what should be recorded?
- Country or region, dates and length of stay.
- Hotel, camping, swimming, bites or contact with animals.
- Associated digestive symptoms or fever.
Serology and parasite tests are not routine. They are requested when the destination, symptoms or eosinophilia make them relevant.
Medicines: an essential question
A medicine may cause itching even without a rash. Note new treatments, dose changes, injectable medicines, occasional treatments, over-the-counter products, supplements and herbal remedies.
What about ‘hormonal’ conditions?
Some endocrine or metabolic disorders may be associated with itching, including an underactive or overactive thyroid, diabetes and, less commonly, other metabolic disorders. They are not screened for routinely in everyone with itching: the context guides assessment.
When the skin was normal at first
- Dry skin
- Age, winter, frequent showers, thin or rough skin.
- Medicine
- Compatible timing of treatment initiation or change.
- Iron deficiency
- Fatigue, heavy periods, diet or bleeding.
- Liver / bile ducts
- Abnormal blood tests, sometimes jaundice or dark urine.
- Kidney
- Known kidney failure or abnormal blood tests.
- Thyroid / metabolism
- Associated signs and blood tests.
- Neurological cause
- Localised itch, burning, tingling or an electric sensation.
- Infection / parasite
- Specific context, travel, exposure and sometimes eosinophilia.
| Possible cause | Helpful clues |
|---|---|
| Dry skin | Age, winter, frequent showers, thin or rough skin. |
| Medicine | Compatible timing of treatment initiation or change. |
| Iron deficiency | Fatigue, heavy periods, diet or bleeding. |
| Liver / bile ducts | Abnormal blood tests, sometimes jaundice or dark urine. |
| Kidney | Known kidney failure or abnormal blood tests. |
| Thyroid / metabolism | Associated signs and blood tests. |
| Neurological cause | Localised itch, burning, tingling or an electric sensation. |
| Infection / parasite | Specific context, travel, exposure and sometimes eosinophilia. |
Which symptoms should be reported to the doctor?
Some symptoms do not necessarily indicate a serious condition, but they can help select the right tests. In particular, report:
- unexplained fever, marked unusual fatigue, unintentional weight loss or repeated night sweats;
- a persistent or enlarged lymph node;
- jaundice, very dark urine or reduced urine output;
- chronic diarrhoea, persistent abdominal pain or associated neurological symptoms.
Which blood tests may be offered?
For an adult with persistent generalised pruritus and no obvious skin cause, initial tests may include, depending on the context:
- full blood count with differential and ferritin;
- CRP ± ESR;
- creatinine / kidney function;
- AST, ALT, alkaline phosphatase, gamma-GT and bilirubin;
- TSH; blood glucose / HbA1c; sometimes LDH.
Not everyone with itching needs all these tests. Typical scabies or eczema does not require the same assessment as generalised itching without lesions for several months.
What about serology tests?
They are requested only when justified by the context, for example hepatitis B/C, HIV in certain situations, or some parasitic infections after travel. There is no universal infectious-disease panel for itching.
Relief, documentation and preparing for the appointment
Are antihistamines always effective?
No. They are particularly useful for histamine-mediated itching such as urticaria. Many other causes — eczema, cholestasis, kidney disease or neuropathic itch — are not mainly driven by histamine. An ineffective antihistamine therefore does not mean the itching is not real.
What can be done while awaiting a diagnosis?
- Moisturise the skin regularly with an emollient.
- Avoid very hot, prolonged showers and use gentle cleansing products.
- Avoid wool and irritating clothing directly against the skin; keep nails short.
- Prefer cool conditions to heat if this helps.
- Photograph lesions before scratching when possible.
Common misconceptions
- ‘It itches, so it must be an allergy.’
- No. Itching has many causes.
- ‘There are no spots, so it is psychological.’
- False: medicines, dry skin, liver, kidney or thyroid disease, or neurological conditions may be involved.
- ‘My antihistamine does not work, so the itching is not real.’
- False: many forms of itching are not histamine-mediated.
- ‘I have a pet, so it must be responsible.’
- No: it is only one part of the investigation.
- ‘Itching without lesions must mean a serious illness.’
- No. There are many benign causes.
- ‘I can stop my medicines to see what happens.’
- Not without medical advice.
| Misconception | SOS Allergo guidance |
|---|---|
| ‘It itches, so it must be an allergy.’ | No. Itching has many causes. |
| ‘There are no spots, so it is psychological.’ | False: medicines, dry skin, liver, kidney or thyroid disease, or neurological conditions may be involved. |
| ‘My antihistamine does not work, so the itching is not real.’ | False: many forms of itching are not histamine-mediated. |
| ‘I have a pet, so it must be responsible.’ | No: it is only one part of the investigation. |
| ‘Itching without lesions must mean a serious illness.’ | No. There are many benign causes. |
| ‘I can stop my medicines to see what happens.’ | Not without medical advice. |
Before your appointment: the SOS Allergo checklist
- When did the itching begin? Where did it start? Did the skin look normal initially?
- Daytime, evening or mainly at night? Is anyone else itching?
- Any new medicine, dose change, over-the-counter treatment or supplement?
- Known liver, kidney, thyroid disease or diabetes? Recent travel? Animals? Occupational exposure?
- Associated symptoms and photographs of the first lesions; bring prescriptions and recent blood-test results.
Final message
Itching is a symptom, not a diagnosis. A good timeline, a few photographs and a precise history often guide assessment without unnecessary tests.
Download the validated sheet
Find this guidance in the validated patient document.
You may also want to read
Main references
- Weisshaar E, et al. European S2k Guideline on Chronic Pruritus. Acta Derm Venereol. 2025;105:adv44220.
- Millington GWM, et al. British Association of Dermatologists’ guidelines for generalized pruritus in adults without an underlying dermatosis. Br J Dermatol. 2018;178:34-60.
- Uzun S, et al. Clinical practice guidelines for the diagnosis and treatment of scabies. Int J Dermatol. 2024;63:1642-1656.
- Practical guide for the diagnosis and treatment of localized and generalized cutaneous pruritus. 2024/2025.
Scientific review: September 2026 · sosallergo.fr