Approach to rash in infants and children

A rash is one of the commonest reasons a family brings a child to see you, and it is the presentation that most often makes clinicians feel they are guessing. The mistake is to try to recognise a single disease from its colour or its overall impression. The reliable method is the opposite: describe what you actually see in a structured way, and let the morphology, the distribution and the age of the child narrow the list for you. This page gives you that method, applied from the neonate to the adolescent, and tells you exactly where the danger lies. [1]

Overview & Definition

A rash is any change in the colour, texture or surface of the skin that is widespread or patterned rather than a single isolated lesion. Two terms recur throughout paediatrics. An exanthem is an eruption on the skin surface - the classic childhood "viral rash". An enanthem is the same kind of eruption on a mucosal surface, such as the mouth (for example the Koplik spots of measles or the oral ulcers of hand-foot-and-mouth disease). The distinction matters because an enanthem is a powerful clue to the cause and to several dangerous diagnoses. [5]

What makes a rash hard is that the same disease can look different on different children and on different skin tones, while very different diseases can look alike. The defence against this is a framework rather than a mental picture: rather than asking "what is this rash?", you ask four questions in order. First, is the child sick or well - because the unwell child with a rash is an emergency regardless of what the rash looks like. Second, what is the morphology - what are the individual lesions? Third, what is the distribution and pattern - where are they and how are they arranged? Fourth, what is the context - the age, fever, itch, mucosa, contacts and the tempo. Answer those four and the differential collapses to a short list you can reason about. [1]

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1. [1]Jalalabadi F Common Pediatric Skin Lesions: A Comprehensive Review of the Current Literature. Seminars in plastic surgery, 2016.PMID 27478417
2. [2]Chadha A Common Neonatal Rashes. Pediatric annals, 2019.PMID 30653638
3. [3]Wilson JL Neonatal Dermatology. Primary care, 2025.PMID 40835282
4. [4]Hartman-Adams H Impetigo: diagnosis and treatment. American family physician, 2014.PMID 25250996
5. [5]Saguil A Hand-Foot-and-Mouth Disease: Rapid Evidence Review. American family physician, 2019.PMID 31573162
6. [6]Meza-Romero R Molluscum contagiosum: an update and review of new perspectives in etiology, diagnosis, and treatment. Clinical, cosmetic and investigational dermatology, 2019.PMID 31239742
7. [7]Thompson MJ Clinical recognition of meningococcal disease in children and adolescents. Lancet (London, England), 2006.PMID 16458763
8. [8]Rife E Kawasaki Disease: an Update. Current rheumatology reports, 2020.PMID 32924089
9. [9]Ramien ML Stevens-Johnson syndrome in children. Current opinion in pediatrics, 2022.PMID 35836393
10. [10]Brazel M Staphylococcal Scalded Skin Syndrome and Bullous Impetigo. Medicina (Kaunas, Lithuania), 2021.PMID 34833375
11. [11]Guttman-Yassky E Atopic dermatitis. Lancet (London, England), 2025.PMID 39955121
12. [12]Leung AKC Henoch-Schonlein Purpura in Children: An Updated Review. Current pediatric reviews, 2020.PMID 32384035