The main symptom of molluscum contagiosum (MC) is a number of small spots on the skin.

The spots are usually firm and dome-shaped, with a small dimple in the middle. They're usually less than 5mm (0.5cm) across, but can sometimes be bigger.

They're typically pink or red on white skin or a beige colour on darker skin, although they may have a tiny white or yellow head in the centre. If this head splits (ruptures), a thick yellowy-white substance will be released, which is highly infectious.

It's important not to squeeze the spots, as this will increase the risk of the infection spreading to other parts of the body.

The spots associated with MC are usually painless, although they can sometimes be itchy and some people develop areas of red, dry and cracked skin around them.

Most people have between 20 and 30 spots, although people with a weakened immune system often have more. The spots may develop in small clusters and can be spread across different parts of the body.

They're most often found in the armpit, behind the knees or on the groin.

In a few cases, particularly when it's spread during sexual contact, spots can develop on the genitals and nearby skin.

How the condition progresses

In many cases, the individual spots will start to crust over and heal within 2 months. Some people may experience mild swelling and redness around each spot as it begins to heal.

The spots do not usually leave scars, but they may leave a small area of lighter skin or a tiny pitted mark, particularly if treatment was needed.

As the virus that causes MC can spread to other parts of the body, new spots may develop as the old ones are disappearing. This can result in an episode of MC lasting for quite a long time.

Most cases clear up within around 6-18 months, but the condition can, occasionally, persist for several years.

Treatment for molluscum contagiosum (MC) isn't routinely recommended because most cases clear up on their own in around 6 to 18 months.

If left alone, MC does not tend to result in scarring or cause any symptoms other than spots. Squeezing or scratching the spots can cause pain and bleeding and may increase the chances of scarring. It also increases the risk of spreading the infection.

Many of the treatments available for MC can be painful or upsetting for young children and some may increase the chances of permanent scarring.

Treatment is usually only recommended for adults and older children who have spots that are particularly unsightly and are affecting their quality of life.

Treatment is also be recommended for people with weakened immune systems, as the condition can take several years to clear in these cases.

Topical treatments

There are a number of topical treatments (creams, lotions and ointments) that can be used to treat MC, although there's not enough evidence to know if any particular treatment is more effective than the others.

Potassium hydroxide

Potassium hydroxide is a medicine available in liquid form that can improve MC by breaking down the skin cells infected by the virus, allowing the immune system to tackle it.

The liquid is applied twice a day on each spot. The spots should eventually become inflamed, before healing and disappearing within the next few weeks.

You should stop using the medicine once the spots have started to become inflamed, or after 14 days if the medicine does not seem to be working.

Side effects of potassium hydroxide can include redness and a slight burning or itching sensation, which usually only lasts for a few minutes after the medication is applied.

Podophyllotoxin

Podophyllotoxin comes in liquid form and poisons the cells of the spots. A special application stick is used to draw up the correct dosage of liquid, which is then dripped onto each spot. You may experience some mild irritation.

The treatment needs to be applied for a few days, followed by a few days without treatment. This is referred to as a treatment cycle.

Imiquimod

Imiquimod is a cream that can be used to treat larger spots or large clusters of spots.

Some studies have found that imiquimod is usually only effective when it is used by people with a weakened immune system.It works by stimulating your immune system into attacking the spots.

You apply the cream to the spots, then wash it off after 6-10 hours. This should be done 3 times a week.

It may take several weeks of treatment before you notice an improvement. Common side effects of imiquimod include:

• hard and flaky skin
• redness and swelling of the skin
• a burning or itching sensation after applying the cream
• headache 

These side effects are usually mild and should pass within 2 weeks of stopping treatment.

Benzoyl peroxide

Benzoyl peroxide is usually available in cream or gel form. It's applied to the spots once or twice a day, after washing and drying the affected area. Use benzoyl peroxide sparingly, because too much can harm your skin.

Benzoyl peroxide makes your skin more sensitive to sunlight, so either avoid excessive exposure to sunlight and ultra-violet (UV) ligh such as sunbeds or sunlamps, or wear sun cream.

Avoid getting the medicine on hair and clothes, as it can bleach them. Wash your hands thoroughly after you finish applying the medicine.

Common side effects of benzoyl peroxide include:

• dry and red skin
• a burning, itching or stinging sensation
• some peeling of the skin

These side effects are usually mild and should resolve after the treatment has finished.

Tretinoin

Tretinoin is available as a liquid that's applied once or twice a day to individual spots. As with benzoyl peroxide, tretinoin can make your skin sensitive to sunlight and UV light.

Tretinoin is not suitable for use during pregnancy because it can cause birth defects. It's important to use a reliable method of contraception while taking tretinoin if you're a sexually active woman.

The most common side effects of tretinoin are mild irritation and stinging of the skin. It may take several months before you notice an improvement in your symptoms.

Other treatments

There are a number of minor procedures that can help remove or destroy MC spots.

They can be painful, so are not generally suitable for children. They must always be carried out by a suitably qualified healthcare professional.

Cryotherapy

Cryotherapy involves freezing the spots with liquid nitrogen to remove them. Each spot is frozen for 5-10 seconds, so that a layer of ice forms over the spot and surrounding skin.

You may need several sessions of cryotherapy before each spot clears completely. You'll need to wait 2 to 3 weeks between each treatment session.

Diathermy

Diathermy uses heat to remove the spots. The area being treated is numbed with a local anaesthetic and a heated electrical device is used to burn off the spots.

Curettage

Curettage removes spots by scraping them off with a thin, metal, spoon-like instrument called a curette. As with diathermy, you may have a local anaesthetic before having this type of treatment.

Pulsed-dye lasers

Pulsed-dye laser treatment is a relatively new type of treatment for MC. It uses a powerful beam of light to destroy the cells that make up each spot. 

You may experience some skin discolouration and discomfort in the treated areas, but this should improve within a few weeks. The procedure may need to be repeated several times to clear all of your spots.

Pulsed-dye laser treatment uses expensive equipment and its availability on the NHS is limited. You'll probably have to pay privately for the treatment, which can be expensive.