Rashes – the ones that need a doctor today
Most rashes are harmless and settle. A few are emergencies, and they are recognisable. What to look for, and what to do meanwhile.
The rashes that cannot wait
The glass test is worth knowing by heart. Press a clear glass firmly against the rash — most rashes blanch and disappear under the pressure. One that stays visible is bleeding under the skin, and with fever that is an emergency.
Rash with new medication
A rash that appears after starting a new medicine — commonly an antibiotic, an anticonvulsant or an HIV medicine — should always be reported rather than treated at home. Most drug rashes are mild, but a small number progress to severe skin reactions that are life-threatening.
The common, non-urgent ones
- Contact dermatitis — red, itchy, sometimes blistered, in the shape of whatever touched it. Soap, nickel, plants, cosmetics.
- Hives — raised, intensely itchy weals that move around and come and go within hours. Often no cause is found.
- Fungal infection — ring-shaped with a raised scaly edge and clearer centre, on the body, groin or feet.
- Scabies — intense itch, worse at night, in the finger webs, wrists and waistline, usually with others in the household affected.
- Heat rash — tiny itchy bumps where sweat is trapped, common in South African summers.
- Eczema and psoriasis, which are long-term patterns rather than one-off rashes.
Commonly used for itch and mild rashes:
Hydrocortisone Cream — Hydrocortisone Lennon, Dermacort, Cortaid, HC45
Mild eczema; dermatitis; insect bites; nappy rash
Cetirizine — Zyrtec, Texa, Adco-Cetirizine, Allerclear
Allergic rhinitis; urticaria; allergic conjunctivitis
Loratadine — Clarityne, Lorano, Adco-Loratadine, Allertin
Allergic rhinitis; urticaria; allergic skin conditions
Calamine Lotion — Calamine
Itching (pruritus); sunburn; insect bites; chickenpox; mild skin irritation
Aqueous Cream BP / Emollient — Aqueous Cream Lennon, E45, Epizone
Dry skin; eczema (as emollient/moisturiser and soap substitute)
Meanwhile
- Stop anything new that touched the skin — a soap, cream, cosmetic or detergent.
- Cool the skin. A cool shower or a cool damp cloth beats scratching.
- Keep it moisturised with a plain emollient; dry skin itches more.
- Take a non-drowsy antihistamine for itch.
- Photograph it. Rashes change, and a photo of what it looked like at its worst is genuinely useful to a clinician.
- Keep nails short — scratching causes the infection that turns a simple rash into a complicated one.
Common questions
- Can I put a steroid cream on any rash?
- No. On a fungal infection it makes things worse and disguises the picture, and strong steroids on the face thin the skin. Mild hydrocortisone on a clearly inflammatory itchy rash for a few days is reasonable; anything unclear or persistent should be seen.
- Is a rash with fever always serious?
- Not always — many childhood viral illnesses cause exactly that and settle. But it is the combination that warrants assessment, particularly with the glass test, drowsiness, a stiff neck or a very unwell-looking child.
- How do I know if a rash is infected?
- Increasing redness spreading outwards, warmth, swelling, pain, yellow crusting or pus, or a fever. Those need treatment rather than more cream.
Sources
- Primary Healthcare Standard Treatment Guidelines and Essential Medicines ListNational Department of Health, South Africa
- Communicable disease surveillance and clinical guidanceNational Institute for Communicable Diseases, South Africa
Last reviewed 4 August 2026.