Impetigo vs Molluscum
Impetigo is a bacterial skin infection that weeps and crusts. The sores are wet, and they dry into a golden-yellow crust that looks like dried honey. Molluscum is a viral infection that makes firm, dry bumps. They are smooth and pearly, with a small dimple on top, and they do not ooze. Impetigo spreads over days and is treated with an antibiotic. Molluscum sits for months and often needs nothing.
What it is
Group A streptococcus or staph bacteria get through a small break in the skin — a scratch, a bite, a patch of eczema — and multiply in the surface layer.
A virus from the pox family infects skin cells and fills each bump with a soft white core. Nothing is infected below the surface.
What it looks like
It starts as a small red patch or blister, breaks open, weeps, and dries into a thick yellow crust. Lift a crust and the skin underneath is raw and moist.
Firm, dome-shaped and dry, skin-coloured or slightly pink. The small pit in the middle is the most useful sign.
Size
A single sore can grow from a few millimetres to a coin-sized patch within a week, with new sores appearing around it.
Each bump stays roughly the size of a pinhead or a small bead. The number of bumps grows, not the size of them.
Does it itch or hurt
Scratching is how it moves to new skin, which is why the sores often appear in a line or a cluster.
Some bumps itch. A scratched one turns red and sore, and that red ring often means it is about to clear.
Where it shows up
Classically the face, especially near the nostrils and lips, then the hands, arms and anywhere skin is already broken.
Chest, tummy, sides, armpits, the crooks of the elbows and the backs of the knees.
What it does over time
Untreated, it keeps opening new sores and can stay contagious for weeks. With an antibiotic it usually settles within about a week.
Bumps clear on their own in about 6 to 18 months. New ones keep arriving while old ones fade, so the crop looks endless for a while.
How it is treated
An antibiotic ointment such as mupirocin or fusidic acid for a small patch. Tablets when it is widespread. It stops being contagious about a day after treatment starts.
Most children are left alone, because the bumps go anyway and the treatments can sting or mark the skin. Single bothersome bumps can be scraped or frozen.
When it needs a doctor
Impetigo does not reliably clear on its own, and treatment shortens it and stops it spreading to others.
Worth a visit if bumps are near the eyelid, if one becomes hot and swollen with spreading redness, or if the diagnosis is not clear.
Wet and crusted, or dry and firm
Impetigo is wet: Something is coming out of it. The golden crust is dried fluid, and if you catch a sore early it is a blister or a raw patch rather than a bump.
Molluscum is dry: Nothing weeps from it and nothing crusts over. It is a firm bead sitting in the skin, and the surface over it looks like normal skin.
Speed is the other clue
Impetigo changes day to day: A parent can point to when it started, and the picture on Friday looks worse than the picture on Monday. That pace is bacterial.
Molluscum changes month to month: Nobody remembers when the first bump appeared. New ones drift in slowly over weeks, which is why it is often noticed in the bath rather than on the day it began.
They turn up together more often than you would think
A scratched molluscum bump can become impetigo: The scratch breaks the skin, and broken skin is exactly where these bacteria get in. So one crusted, weeping spot in a crop of otherwise dry bumps usually means both.
The treatment then splits: The infected spot needs an antibiotic. The rest of the bumps still need nothing. Treating the whole crop with antibiotic cream does not shorten the molluscum.
Keeping either one from travelling
Impetigo travels on towels, bedding and hands: Separate towels, a change of bedding, and short nails all help. Children are usually kept off school until about 24 hours after treatment starts, or until the sores have crusted over and dried.
Molluscum travels the same way, more slowly: Separate towels and no shared bath water reduce the spread between brothers and sisters. Children are not kept out of school for molluscum, and covering a bump for swimming or contact sport is enough.
