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Molluscum contagiosum
Not a wart virus but a pox virus — and the central dimple is the sign. The course is measured in months and ends by itself.
Also known as: molluscum contagiosum · molluscs · water warts · pox-virus warts
Open in the tool — with search and all the links →This compilation is for information and replaces neither medical diagnosis nor treatment. If you have symptoms, see a doctor.
Small dome-shaped papules, two to five millimetres, skin-coloured to pearly white, with a fine dimple in the middle. Single or in clusters, often where skin meets skin: armpits, backs of the knees, elbow creases, the side of the trunk, and in children the face as well. Press one open and a whitish, crumbly core comes out. The dimple is what separates it from an ordinary wart: that one is rough, horny, has no depression, and comes from an entirely different virus. Molluscum is caused by a pox virus that lives only in the outer skin and nowhere else in the body.
It mainly affects children between two and ten. It travels by skin contact, shared towels and bath toys, wet skin while bathing — hence the old name water warts. The second route runs through one’s own hand: scratching spreads the virus along the scratch line, and a row appears like a string of beads. In adults they sit more often in the genital area; the usual route there is sexual contact. Very many lesions at once, lesions clearly larger than a centimetre, or a picture that does not stop for years deserve a look — not because of the molluscum itself, but because the state of the defences behind it can matter.
The decisive figure is time. A single lesion lasts weeks to months; the whole picture clears in most people within six to eighteen months, and in some it takes up to four years. It ends by itself and as a rule leaves no scar. Shortly before the end a lesion often turns red, swollen and crusted — it looks like an infection and is often treated as one, when it is the sign that the defences are clearing the spot. In some children an itchy eczema forms around them; that is the real engine of spread, because it leads to scratching.
Six to eighteen months until they go, longer in some. In the comparisons, at six to twelve months no method is clearly ahead of waiting. Removing buys time — and is paid for in pain, scars or pigment marks. Both are defensible; the choice belongs to whoever carries it.
Treat the surrounding eczema and grease the skin. It is the only step that slows the spread without touching a single lesion. As long as it itches, the number rises faster than any method can lower it.
Swimming, sport and school are not to be avoided. What counts is the barrier: cover the spots with a waterproof plaster or clothing, do not share towel, flannel and bath toys, do not shave the affected field.
The four usual routes. Potassium hydroxide as a five to ten per cent solution is applied at home until the spot inflames; the curette removes at once but hurts and in children usually needs a numbing cream first; freezing takes sessions; cantharidin raises a blister and is applied only in the practice. All four can leave a scar or a pale mark where they were used.
The one sign that carries. A one- to two-millimetre depression on a smooth, dome-shaped top. On very small or very fresh papules it is still missing — then look at the neighbours, one of which usually has one.
An ordinary wart is horny, rough and often carries black dots — thrombosed vessels. A molluscum shines, feels smooth and has no dots. The difference is visible to the naked eye, and two different viruses stand behind it.
Where the papules stand in a line, one’s own hand put them there. A razor blade over the affected field does the same. That is not a chance pattern but the commonest way three spots become thirty.
Just before a lesion goes, it becomes inflamed. It looks like a bacterial infection and is often treated as one. If it affects single spots and turns to a crust within one to two weeks, it is the finish. Purulent spread with fever is something else and should be seen.
In some children an itchy, scaling field forms around the papules. It is not the spread itself but its engine: it itches, the child scratches, and the virus goes along. Treating that eczema takes the drive out of the spread.
In adults molluscum almost never comes singly and almost never on the face without reason. A single pearly lesion that slowly grows over months and does not go is therefore a reason to have it looked at — not because that is usual, but because the mix-up here runs the other way.
Tested in a small trial in thirty children over four weeks, combined with iodine; the combination lowered the lesion count more clearly than iodine alone, with the oil alone in between. A trial of that size carries no recommendation. Undiluted it irritates a child’s skin, and irritated skin gets scratched — which here does the opposite of what is wanted.
Not against the virus but against the scratching: a greasy base settles the eczema around them. That is the point where a plain ointment does more than a product aimed at the papules.