The patient with a new rash: a case-based approach

The presentation

Picture a young adult who develops a widespread rash of small pink spots over a few days. They feel mildly unwell with a slight temperature but are eating, drinking and behaving normally. The rash fades briefly when pressed. This is a common, generally reassuring picture — a widespread rash in someone who is otherwise well often follows a simple viral infection or a reaction to something. Now picture a different scenario: a person who feels very unwell, with a fever, a stiff neck, dislike of bright light and a spreading rash of dark red or purple spots that do not fade when pressed. That second story is a medical emergency. The way someone looks and feels overall matters just as much as the rash itself.

Describing the rash

Clinicians describe a rash before they name it. Is it flat or raised? Are the spots small like pinpricks or larger blotches? Is it itchy, painful or numb? Where did it start and how is it spreading? Two features are especially important. First, does it blanch — does it fade when you press a clear glass against it? A rash that does not fade (non-blanching) can mean bleeding under the skin and needs urgent attention. Second, are the lips, tongue, eyes or genitals involved, and is the skin blistering or peeling? Involvement of these moist surfaces or widespread blistering points towards serious drug reactions or severe infections that need emergency care.

The reassuring patterns

Many new rashes are harmless. Viral rashes are common, especially in children, and appear as widespread pink spots in someone with a mild cold or temperature; they fade over days. Hives (urticaria) are raised, intensely itchy welts that come and go within hours and are usually an allergic-type reaction — troublesome but rarely dangerous on their own. Eczema and contact dermatitis cause dry, itchy, inflamed patches, often where skin has touched an irritant. Fungal infections cause ring-shaped, scaly patches. These conditions share reassuring features: the person is otherwise well, the rash blanches, and there is no involvement of the mouth or eyes, no blistering and no rapid deterioration. They can usually be managed in the community.

The red flags

A small number of rashes signal serious illness. A non-blanching rash — spots or bruise-like patches that do not fade under pressure — alongside fever, headache, neck stiffness or feeling very unwell can indicate meningococcal infection and is an emergency. A rash with facial or tongue swelling, breathing difficulty or wheeze may be anaphylaxis. Widespread blistering or peeling skin, or a rash affecting the lips, mouth and eyes, especially after starting a new medicine, may be a severe drug reaction. A rapidly spreading, very painful red area with fever can suggest a deep skin infection. Any rash in someone who looks seriously ill, is drowsy or is struggling to breathe needs emergency assessment without delay.

The safe pathway

The practical approach mirrors the red eye: match the urgency to the danger signs, not the appearance alone. A new rash in someone who feels well, that blanches and does not involve the mouth or eyes, can usually be assessed by a pharmacist, GP or NHS 111. Persistent or spreading rashes, or those with mild systemic symptoms, deserve a clinical review. But a non-blanching rash with fever, difficulty breathing, facial swelling, widespread blistering, or a person who looks very unwell or is drowsy needs 999 or A&E straight away. The glass test is a useful tool, but it is not perfect — if you are worried about someone who is deteriorating, seek help regardless of what the rash looks like.