12.5 Skin Infections, Infestations, Childhood Rashes & Skin Cancer
Key Takeaways
Cellulitis is treated with flucloxacillin for 5–7 days (NICE NG141), with clarithromycin or doxycycline in penicillin allergy; bilateral red legs are rarely cellulitis.
Localised non-bullous impetigo is treated first with hydrogen peroxide 1% cream; widespread impetigo or systemic illness needs oral flucloxacillin (NICE NG153).
Scabies is treated with permethrin 5% cream applied twice, 1 week apart, with all household and close contacts treated at the same time.
Measles causes fever, cough, coryza, conjunctivitis and Koplik spots before a rash spreading from the face downward, and is a notifiable disease.
Basal cell carcinomas grow slowly with a pearly rolled edge and rarely metastasise, whereas squamous cell carcinomas grow faster and need a suspected cancer pathway referral.
Skin Infections, Infestations, Childhood Rashes & Skin Cancer
Bacterial Skin Infections
Cellulitis & Erysipelas (NICE NG141)
- Cellulitis: spreading, hot, tender erythema and swelling of the dermis and subcutaneous tissue, usually one leg, often with an entry point (tinea pedis, wound, ulcer). Erysipelas is a more superficial infection with a sharp, raised border. Both are usually caused by Streptococcus pyogenes or Staphylococcus aureus.
- Treatment: flucloxacillin (500 mg–1 g four times daily) for 5–7 days; clarithromycin or doxycycline in penicillin allergy (erythromycin in pregnancy); co-amoxiclav for cellulitis near the eyes or nose. Mark the edge to monitor spread. Admit for systemic illness, rapid spread, orbital involvement or failure of oral treatment.
- Mimics: bilateral red legs are rarely cellulitis; consider venous eczema, lipodermatosclerosis, oedema and DVT.
- Necrotising fasciitis (pain out of proportion, rapid spread, systemic toxicity) is a surgical emergency (section 12.1).
Impetigo (NICE NG153)
Highly contagious superficial infection, common in children, with golden-crusted lesions (non-bullous) or flaccid blisters (bullous, S. aureus).
- Localised non-bullous: hydrogen peroxide 1% cream first; topical fusidic acid if unsuitable.
- Widespread, bullous or systemically unwell: oral flucloxacillin for 5–7 days (clarithromycin if allergic).
- Exclude from school or nursery until lesions are crusted and healed, or 48 hours after starting antibiotics.
Fungal Infections
- Tinea (ringworm): annular scaly plaques with central clearing (corporis), interdigital maceration (pedis) or scaling scalp patches with hair loss (tinea capitis, which needs oral treatment such as terbinafine or griseofulvin). Confirm with skin scrapings. Topical azoles or terbinafine treat most skin infections; fungal nail infection needs nail clippings before oral terbinafine.
- Candida: red, moist rash with satellite lesions in skin folds; topical azoles.
- Pityriasis versicolor: hypo- or hyperpigmented scaly patches on the trunk (Malassezia); ketoconazole shampoo.
Viral Skin Infections
- Herpes zoster (shingles): painful dermatomal vesicular rash. Give oral aciclovir or valaciclovir within 72 hours (especially if over 50, immunocompromised or with severe pain or ophthalmic involvement). Vesicles on the tip of the nose (Hutchinson's sign) suggest ophthalmic zoster, needing same-day ophthalmology review. The shingles vaccine (Shingrix) is offered to older adults and immunosuppressed people in the UK programme.
- Herpes simplex, molluscum contagiosum (pearly umbilicated papules; self-limiting) and viral warts are common and usually self-limiting.
Infestations
Scabies
Sarcoptes scabiei mites cause intense itch, worse at night, with burrows in finger web spaces, wrists, genitals and around the nipples; other household members are often itchy.
- Permethrin 5% cream applied to the whole body (including the scalp and face in young children and older people), washed off after 8–12 hours, and repeated after 7 days. Malathion is an alternative.
- Treat all household and close contacts at the same time, and wash bedding and clothes on a hot cycle.
- Itch can persist for 2–4 weeks after successful treatment.
- Crusted (Norwegian) scabies in immunosuppressed or frail people is highly infectious and needs oral ivermectin and outbreak control.
Head Lice
Diagnose by finding live lice on detection combing. Treat with wet combing or a physical insecticide such as dimeticone 4%, repeated after 7 days. Treat only those with live lice; school exclusion is not needed.
Childhood Exanthems
| Infection | Key Features | Exclusion & Notes |
|---|---|---|
| Measles | Fever, cough, coryza, conjunctivitis, Koplik spots (white spots on the buccal mucosa), then maculopapular rash starting behind the ears and on the face and spreading down | Notifiable; exclude for 4 days from rash onset; complications: pneumonia, otitis media, encephalitis, subacute sclerosing panencephalitis |
| Chickenpox (varicella) | Itchy crops of papules, vesicles and crusts at different stages, mainly on the trunk | Exclude until all lesions have crusted (usually about 5 days); avoid ibuprofen; aciclovir for adults, neonates, immunosuppressed; exposed non-immune pregnant women need urgent advice |
| Scarlet fever | Sore throat, fever, sandpaper-like rash, strawberry tongue, flushed cheeks with circumoral pallor | Notifiable; phenoxymethylpenicillin for 10 days; return 24 hours after starting antibiotics |
| Slapped cheek (parvovirus B19) | Bright red cheeks, then a lacy rash on the limbs | Infectious before the rash, so no exclusion; risk of aplastic crisis in haemolytic anaemias and fetal hydrops in pregnancy (seek advice if exposed before 20 weeks) |
| Roseola infantum (HHV-6) | High fever for 3–4 days, then a rash as the fever settles | Febrile seizures possible |
| Hand, foot and mouth disease | Mouth ulcers and vesicles on the hands and feet (coxsackievirus) | Self-limiting; no exclusion needed if well |
| Rubella | Mild illness, rash and post-auricular lymphadenopathy | Notifiable; congenital rubella syndrome in early pregnancy |
Skin Cancer & Premalignant Lesions
| Lesion | Appearance | Behaviour | Referral & Treatment (NICE NG12) |
|---|---|---|---|
| Actinic keratosis | Rough, scaly patches on sun-exposed skin | Premalignant | Sun protection; topical 5-fluorouracil, imiquimod or cryotherapy |
| Bowen's disease (SCC in situ) | Slowly enlarging red scaly plaque | Can become invasive SCC | Topical treatment, cryotherapy or excision |
| Basal cell carcinoma | Pearly nodule with rolled edge and telangiectasia, may ulcerate (rodent ulcer) | Slow, locally invasive, rarely metastasises | Routine referral usually; urgent if size or site (for example near the eye) is a concern; surgical excision, Mohs surgery on the face |
| Squamous cell carcinoma | Rapidly growing, keratotic or ulcerated nodule; immunosuppressed and transplant patients at high risk | Can metastasise | Suspected cancer pathway referral |
| Melanoma | Changing pigmented lesion (ABCDE; weighted 7-point checklist) | Metastasises early | Suspected cancer pathway referral (section 12.1) |
Advise everyone about sun protection (shade, clothing, high-factor sunscreen) and avoiding sunbeds.
Other Common Skin Conditions
| Condition | Key Features | Management |
|---|---|---|
| Contact dermatitis | Irritant (most common; soaps, wet work) or allergic (type IV reaction to nickel, fragrances, rubber, hair dye) eczematous rash at the contact site | Identify and avoid the cause (patch testing for suspected allergy), emollients, topical corticosteroids |
| Hidradenitis suppurativa | Recurrent painful nodules, abscesses and sinus tracts in the axillae, groin and under the breasts; linked to smoking and obesity | Weight loss, stopping smoking, long courses of oral tetracyclines, biologics or surgery for severe disease |
| Folliculitis | Itchy or tender pustules centred on hair follicles (often S. aureus) | Hygiene, antiseptic washes; topical or oral antibiotics if extensive |
| Infantile haemangioma | Raised red "strawberry" lesion appearing in the first weeks, growing for months, then slowly involuting | Observation; propranolol (specialist) for lesions threatening vision, the airway or feeding, or ulcerating |
| Lichen planus | Itchy, purple, polygonal, flat-topped papules on the wrists and shins with white lace-like Wickham's striae; oral white lacy lesions | Potent topical corticosteroids; review oral lesions (small malignancy risk) |
| Lipoma | Soft, mobile, painless subcutaneous lump | Reassure; refer for imaging if larger than about 5 cm, growing, painful, deep or recurrent (to exclude sarcoma; NICE NG12 advises an urgent ultrasound for an unexplained enlarging soft tissue mass) |
Skin signs of systemic disease include acanthosis nigricans (velvety pigmentation in skin folds with insulin resistance or, rarely, gastric adenocarcinoma), livedo reticularis (lacy mottling with antiphospholipid syndrome or vasculitis), erythema nodosum (sarcoidosis, streptococcal infection, IBD, TB, pregnancy) and non-blanching petechiae or purpura (sepsis, thrombocytopenia, vasculitis), which need urgent assessment.
A 4-year-old boy has three small honey-crusted lesions around his mouth. He is well and afebrile. What is the most appropriate first-line treatment according to NICE?
Oral flucloxacillin for 7 days
Oral clarithromycin for 5 days
Hydrogen peroxide 1% cream
Topical mupirocin for 14 days
A 30-year-old woman has 3 weeks of intense itching, worse at night, with excoriated papules in her finger web spaces and wrists. Her partner is also itchy. What is the most appropriate management?
Permethrin 5% cream for her alone, applied once to the whole body
Permethrin 5% for her and her partner together, repeated after 7 days
Oral antihistamine and emollients, reviewing in 2 weeks if still itchy
Oral flucloxacillin for secondary infection of the excoriations
A 3-year-old unvaccinated child has 4 days of fever, cough, runny nose and red eyes, followed by a red maculopapular rash that began behind the ears and spread down the body. White spots are seen on the buccal mucosa. What is the most appropriate action?
Reassure the parents, as this is roseola infantum caused by HHV-6
Exclude from nursery until all of the skin lesions have crusted over
Start oral penicillin V and exclude from nursery for 24 hours
Notify health protection and exclude for 4 days from rash onset
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