What Is That Weird Bump on My Kid?

There are many universally shared parenting experiences — poop blowouts, for example, or the refusal to put on shoes. I’d argue that finding weird bumps on your kid is one of them. Sometimes the bump is a tick. Sometimes it’s a stick-on jewel from an art kit (how it got on their butt? Best not to ask).

There are times, though, when you don’t know what the bump is and you end up at the pediatrician, and maybe you hear something that sounds scary. The good news is that these bumps are generally harmless and self-limiting (go away on their own), but it’s easier to accept that if you have the full information.

Here, a primer on two of the more common types of weird child skin bumps: molluscum contagiosum and warts.

Molluscum contagiosum

What is it?

Molluscum contagiosum is a viral infection (caused by the molluscum contagiosum virus) that causes skin-colored, dome-shaped bumps, called lesions. The bumps can appear anywhere on the body except the palms and the soles of the feet, and they are small, typically 2 to 5 millimeters in diameter.

Although you may not have heard of this virus (at least until your child gets it), it is common. The prevalence in children is estimated at 5% to 10%.

How do you get it?

The virus spreads through contact — someone scratches a sore, or touches someone else — or through shared materials. Swimming, perhaps through shared towels, is one of the key risk factors. Kids who have eczema may also be at higher risk, and sometimes the lesions appear along with an eczema outbreak at the same location.

If you have one child who has it, there is a reasonable chance they will spread it to a sibling. You can lower the risk by not having children share towels or rub against each other, and, of course, by washing hands.

Diagnosis is through a visual examination of the bumps (photos here). It’s possible to get fancier and biopsy the bumps to look for the particular virus, but this would be very unlikely unless there were other concerns.

How is it treated?

For most children, the first-line treatment is nothing. If you are not immunocompromised, individual lesions will generally disappear within a couple of months, with the entire episode ending after 6 to 12 months.

There are more immediate treatment options if a faster resolution is needed for some reason. One approach is to cut the lesions off. In a sample of about 2,000 children, more than half of them between 2 and 5 years old, researchers showed that 70% of cases were cured after a single visit and 26% more after two visits. This procedure is simple — literally, the bumps are cut off. Healing is typically easy, although for kids, the experience may be very scary.

A second option is a blistering compound, cantharidin, that is applied to the lesions. The lesions are then wrapped, and the goal is that they blister and then are eliminated. Randomized trial data shows efficacy here, but not as high as with cutting; slightly less than half of cases resolve with a single treatment. A retrospective analysis of medical charts showed better resolution, as high as 90%, with multiple visits.

Given that the virus is self-limiting, there is some debate as to whether treatment should be offered. If your child has this and they are really bothered by it, it’s worth asking.

Warts

What are they?

Warts (scientific name: verrucae) are caused by the human papillomavirus (HPV), which has many subtypes; many warts on children are caused by HPV-1. (You may be more familiar with HPV as an STD — genital warts are most commonly caused by several other HPV strains.)

The most common type of wart in children is a cutaneous wart, which includes common warts, plantar warts, and flat warts, all of which look slightly different.

Warts are common in kids, though estimates of the prevalence vary widely. Using interview data from the U.S., about 5% of children are estimated to have had warts in a year. On the other hand, one study of Dutch children found that 44% of them had at least one wart. Elementary school children seem to be at the highest risk.

Warts are generally diagnosed through visual examination, although there are a number of other skin features that may appear (to a non-specialist) to be similar. This includes corns, skin tags, and less common conditions with names like lichen planus. Your doctor or dermatologist should be able to tell if a bump is a wart or something else.

How do you get them?

Warts are contagious. HPV can be spread through direct skin contact, and people may carry this virus asymptomatically. The need for direct contact means warts can be spread in classrooms of younger children and within families. Having said this: many people carry the HPV-1 virus on their skin and only some develop warts, so treating the warts does not necessarily limit spread.

How are they treated?

For kids, warts can be self-limiting; in about two-thirds of cases, they resolve on their own within a couple of years.

However, a lot of people do not want to wait for this, and there are various other, more aggressive options. In fact, there are a lot of these options, and they are generally used in order.

The first-line treatment: salicylic acid or silver nitrate, which seems to increase resolution by something like 30 percentage points. These treatments involve a daily topical therapy, often for up to 12 weeks. Side effects include skin irritation and sometimes pain.

If that doesn’t work, the typical second-line option is freezing. This can be done either by a doctor or at home, and the exact approach varies. Meta-analysis data are not strongly supportive of cryotherapy alone, although aggressive cryotherapy or cryotherapy combined with salicylic acid seems to work better. Still, only a little over half of warts are cured in this way.

If these approaches do not work and there is still a desire to remove the warts, there are a variety of other options. These range from chemotherapy-based solutions to injecting the warts with the mumps antigen. Covering the wart with duct tape for a week is a low-risk approach with varying evidence on efficacy. If you get to this place, you’ll want to talk through options with your doctor. Many options have a bit of evidence on efficacy; few have anything very compelling.

Or you could just wait! Wart treatment, for kids in particular, can be painful and scary. If the warts are not bothering them, “do nothing” may be the best option.