What should you know about vasculitic rash causes?

Small-vessel inflammation may produce red or purple spots that do not fade when pressed, raised purplish bumps, burning, tenderness, or swelling. Possible triggers include an infection, a medicine, an immune response, or a condition affecting blood vessels. The skin pattern alone cannot identify the cause.

Many conditions can mimic part of this appearance. Itchy eczema may resemble [Atopic Dermatitis](/conditions/atopic-dermatitis/), while exposure-related irritation may be [Contact Dermatitis](/conditions/contact-dermatitis/). A new medicine can cause a [Drug Rash](/conditions/drug-eruption/). Other look-alikes include [Heat Rash](/conditions/heat-rash/), [Intertrigo](/conditions/intertrigo/), [Psoriasis](/conditions/psoriasis/), [Ringworm](/conditions/ringworm/), and [Scabies](/conditions/scabies/).

Take clear photographs as the rash changes, note when it began, and list recent medicines, infections, foods, travel, and new skin products. Do not stop a prescribed medicine without advice, but contact the prescriber promptly if the rash began after a new drug. Avoid scratching and use gentle, fragrance-free skin care until assessed.

A clinician may examine whether spots blanch, feel raised, or involve the legs and feet. Blood or urine tests and sometimes a small skin sample may be considered when vasculitis is suspected. Treatment depends on the confirmed cause rather than the colour alone.

Seek urgent medical care for a rapidly spreading rash with fever, facial or tongue swelling, breathing difficulty, faintness, severe pain, blistering, skin peeling, blood in the urine, marked abdominal pain, or new weakness. Arrange prompt review for purple spots that do not fade with pressure, especially if they are accompanied by joint pain, swelling, or feeling unwell.

Could this be vasculitis or a more common rash that looks similar? Do my recent medicines, infection symptoms, or medical history change the assessment? Do I need tests or a skin sample, and which symptoms should send me to urgent care?