In short
A rash that stays visible when you press on it is bleeding into the skin rather than redness of the skin. When those spots are raised and sit mainly on the lower legs, small-vessel vasculitis is one of the main explanations — and whether it is a self-limiting skin problem or the first sign of something affecting the kidneys depends on tests that should be done promptly.
Reviewed by Dr. Ashish Baweja, DM Clinical Immunology & Rheumatology, AIIMS Rishikesh · last updated October 2026
Most rashes fade when you press them. The redness is blood inside vessels, and pressing empties the vessels briefly.
A rash that stays visible under pressure is different: blood has leaked out of the vessels into the skin, and it cannot be squeezed away. The simplest way to check is the glass test — press the side of a clear glass firmly against the rash and look through it.
This is widely known in the context of meningitis, and quite right too. But it is also the key finding in a group of conditions a rheumatologist sees often.
What raised, non-blanching spots mean
When the spots are not only non-blanching but also raised — you can feel them with a fingertip, like small grains under the skin — the term is palpable purpura, and it is close to a diagnosis in itself. It means inflammation of small blood vessels in the skin, which is cutaneous small-vessel vasculitis.
The typical appearance:
- Small purple-red spots, a few millimetres across, sometimes merging
- Mostly on the lower legs and ankles, often symmetrical, sometimes on the buttocks
- Worse after standing for long periods — gravity matters, because pressure in the leg vessels is highest there
- Appearing in crops over days
- Fading through the colours of a bruise, sometimes leaving brown staining
It may itch, burn or be mildly painful, and it is often not very uncomfortable at all, which is why people wait.
The causes
Small-vessel vasculitis is a reaction pattern rather than a single disease. The common triggers:
- Infection — a recent throat or chest infection is one of the commonest, particularly in children and young adults
- Medicines — antibiotics, NSAIDs, some diuretics and anti-epileptics, usually starting one to three weeks after beginning the drug
- IgA vasculitis (formerly Henoch–Schönlein purpura) — rash plus joint pain, abdominal pain and, importantly, possible kidney involvement. See IgA vasculitis
- Autoimmune disease — lupus, rheumatoid arthritis, Sjögren's syndrome
- ANCA-associated vasculitis — a systemic illness affecting lungs and kidneys as well as skin; see ANCA-associated vasculitis
- Cryoglobulinaemia, often linked to hepatitis C — see cryoglobulinaemic vasculitis
- Blood disorders and, uncommonly, malignancy
In a proportion of cases no cause is ever found, and the rash settles by itself over weeks.
What makes it urgent
The rash itself is rarely the dangerous part. What matters is whether the same process is affecting organs that do not announce themselves.
Seek care the same day if the rash comes with:
- Fever and feeling genuinely unwell
- Blood in the urine, frothy urine, or reduced urine output — kidney involvement is often silent until it is advanced, which is why a urine test is essential
- Coughing blood or breathlessness
- Severe abdominal pain, or blood in the stool
- Numbness or weakness in a hand or foot, such as a foot that drops — nerve involvement
- Skin ulceration or black areas, meaning tissue is losing its blood supply
- A rash that is spreading rapidly
And separately, urgently: a non-blanching rash with fever, headache, neck stiffness or confusion needs emergency assessment for meningococcal infection. That is a different illness and it moves in hours.
The tests that should be done
A short list does most of the work, and the urine test is the one not to skip:
- Urine dipstick for blood and protein — the cheapest test here and the one that decides urgency. It can be done in minutes.
- Full blood count, including platelets — low platelets cause a non-blanching rash that is flat rather than raised, and is a different problem.
- Kidney function and ESR/CRP — see what ESR and CRP prove.
- ANA, ANCA, rheumatoid factor, complement levels, depending on the picture.
- Hepatitis B and C, particularly where cryoglobulinaemia is suspected.
- A skin biopsy, best taken from a fresh lesion less than 48 hours old. It confirms the vasculitis and, with immunofluorescence, identifies IgA deposition.
Flat versus raised
Worth separating, because they point in different directions.
Flat non-blanching spots (petechiae) suggest a problem with platelets or clotting — low platelet count, or a clotting disorder. These need a blood count urgently.
Raised non-blanching spots (palpable purpura) suggest inflammation of the vessel wall — vasculitis.
A doctor will want to feel the rash, not just look at a photograph, which is one reason a video consultation is less useful here than a visit.
Treatment
It depends entirely on the cause and on whether anything beyond skin is involved.
- Skin only, with a trigger identified — stop the offending medicine, treat the infection, elevate the legs, compression stockings, and time. Many cases settle within weeks without immunosuppression.
- Significant symptoms, skin only — a short course of steroids is sometimes used.
- Organ involvement — kidney, lung, gut or nerve — needs proper immunosuppressive treatment, promptly, because damage accrues.
Avoid standing for long periods while it is active, and keep the legs elevated when you can.
How long it takes to settle
For a skin-limited vasculitis with an identified trigger, the usual course is weeks: crops stop appearing within days of removing the cause, and existing spots fade over two to six weeks, often leaving brown staining that takes months to go.
Some people have recurring episodes over months, particularly where no cause is found. That is frustrating rather than dangerous, provided the urine and blood tests stay clear — which is the reason for repeating them rather than assuming.
What should not happen is a rash that is simply watched indefinitely without the urine ever being checked. Kidney involvement is silent, and it is the single thing that changes the management of an otherwise unremarkable rash.
What to do while it is active
Practical measures that help, and are usually all that is needed for skin-limited disease:
- Elevate the legs when sitting. Pressure in the lower leg vessels is what drives the distribution, and raising them reduces new crops.
- Avoid long periods of standing. This is the most reliable aggravating factor.
- Compression stockings, if advised and if arterial circulation is adequate.
- Stop the suspected medicine — but only in discussion with the prescriber if it is something important.
- Do not scratch or burst any blistered areas; broken skin on the lower leg heals slowly and is a route for infection.
- Photograph each new crop with the date, which is far more useful to a doctor than a description of what it looked like last week.
What to do now
If you have a rash on your lower legs:
1. Do the glass test. If it fades, it is almost certainly not this.
2. Feel it. Raised or flat changes the likely cause.
3. Photograph it, with a date — these rashes come in crops and may have faded by the appointment.
4. List every medicine started in the last month, including over-the-counter painkillers.
5. Get a urine test, even if you feel completely well. This is the step most often skipped and the one most likely to change management.
If you have a non-blanching rash and have not had your urine checked, that is the gap worth closing quickly. You can request a callback or book a consultation.
Common questions
How do I tell if a rash is vasculitis?
Press a clear glass firmly against it. A rash that stays visible under pressure is bleeding into the skin rather than simple redness. If those spots are also raised — you can feel them with a fingertip — and sit mainly on the lower legs, small-vessel vasculitis is likely and needs assessment.
What causes purple spots on the lower legs?
Common causes include a recent infection, a medicine started in the previous one to three weeks, IgA vasculitis, autoimmune disease such as lupus or rheumatoid arthritis, and systemic vasculitis. Low platelets cause a similar but flat rash. In some people no cause is found and it settles on its own.
Is a vasculitis rash dangerous?
The rash itself usually is not. What matters is whether the same vessel inflammation is affecting the kidneys, lungs, gut or nerves, which can happen without symptoms. That is why a urine test for blood and protein is essential even when you feel well.
Why do these rashes appear on the legs?
Pressure in the small vessels of the lower legs is highest, because of gravity. That is also why the rash is worse after long periods of standing and why elevating the legs helps while it is active.
When should a leg rash be seen urgently?
With fever and feeling unwell, blood or froth in the urine, coughing blood or breathlessness, severe abdominal pain, new numbness or weakness in a hand or foot, or skin ulceration. A non-blanching rash with fever, headache or neck stiffness needs emergency care for possible meningococcal infection.
Will the rash leave a mark?
Often it fades through the colours of a bruise and may leave brown staining for months, particularly where crops have recurred. That staining is harmless and usually fades slowly.
Sources
- NHS — vasculitis www.nhs.uk
- American College of Rheumatology — vasculitis rheumatology.org
- DermNet — cutaneous small-vessel vasculitis dermnetnz.org
- NHS — meningitis symptoms and the glass test www.nhs.uk
This article is general information and does not replace a consultation.