see also:

• paediatric exanthems
• localised rashes

1. is the patient in shock or having trouble breathing? - immediate resuscitation as required

• consider:
  • anaphylaxis with/without typical urticaria
  • septic shock including meningococcal septicaemia, staph scalded skin syndrome, etc
  • many less common / rare conditions such as
    • toxic shock syndrome - could there be retained tampons or foreign bodies?
    • Stevens-Johnson syndrome (SJS) and Toxic Epidermal Necrolysis (TEN)
    • tropical diseases such as dengue fever

2. is it purpuric or petechial (ie. non-blanching and leaving a blue-purple mark)

• go to:
  • the petechial rash / purpura
  • Fever with petechial or purpuric rash
  • this may be life threatening meningococcal septicaemia or thrombocytopenia

2. is it vesicular / bullous / blistering?

• go to vesicular rashes - isolate patient case it is varicella-zoster virus (chickenpox/shingles) (chicken pox or herpes zoster), or monkeypox / mpox (MPVX)

3. if red eyes and/or cough, could it be measles? - if so, mask and isolate patient immediately in negative pressure room

• especially if overseas traveller or a contact not vaccinated with prodrome of conjunctivitis, hacking cough then develops m/p rash starting on face then descending down the body on ~ day 5
• a atypical measles CAN occur in those who are vaccinated
• bilateral red eyes may also be due to very contagious adenovirus or early measles

4. are there target lesions present?

• probable erythema multiforme, but see the list of important DDx on that link

5. are there obvious wheals in an asymmetric pattern?

• go to urticaria

6. is it a generalised maculo-papular or macular rash?

• go to:
  • acute generalized non-vesicular non-purpuric rashes covering most parts of the body
  • see also paediatric exanthems