Molluscum contagiosum

Molluscum contagiosum (MC) is a viral infection that affects the skin.

Introduction

Molluscum contagiosum (MC) is a viral infection that affects the skin. It is highly contagious and easily spread.

MC most commonly affects children and young adults, although it can occur at any age.

Usually, the only symptom of MC is a number of small, firm, raised papules (spots) that develop on the skin. They are not painful but may be itchy.

Read more about the spots of molluscum contagiosum.

What causes molluscum contagiosum?

MC is caused by a virus known as the molluscum contagiosum virus (MCV).

Although MC is highly contagious, most people are resistant to the virus. This means they are unlikely to develop the condition if they are exposed to the virus.

MC can be spread through skin-to-skin contact with someone who is infected, or it can be passed on by touching contaminated objects, such as a flannel or towel.

Children can catch MC after coming into close physical contact with another child who is infected, such as while play-fighting or hugging.

Adults can catch MC after having close physical contact with an infected person, such as sexual contact (this doesn't necessarily have to be sexual intercourse).

Read more about how molluscum contagiosum is spread.

At-risk groups

There are three main groups of people who tend to be affected by MC. They are:

  • young children who are one to five years of age
  • people who have had a number of different sexual partners
  • people with a weakened immune system, either due to having a condition such as HIV or AIDs, or from receiving treatment such as chemotherapy

Diagnosing molluscum contagiosum

Visit your doctor if you think you or your child may have MC. Your doctor will examine your skin (or your child's) and ask about any other symptoms.

The spots of MC are usually easy to recognise, so your doctor should be able to diagnose the condition without the need for further tests.

However, if your doctor is not sure whether MCV is responsible, they may want to carry out some tests. For example, they may take a small sample from the centre of one of the spots to test it for MCV.

Read more about how molluscum contagiosum is diagnosed.

Treating molluscum contagiosum

In people who are otherwise healthy, MC usually clears up on its own after 12-18 months. However, in people who are immunocompromised (have a weakened immune system), MC can last much longer.

Routine treatment for MC, particularly in children, does not tend to be recommended because:

  • the infection usually clears up on its own
  • the infection does not usually cause any symptoms other than the spots
  • the infection does not usually interfere with everyday activities, such as going to work, swimming or playing sports
  • many treatments can be painful and may cause scarring or burn the surrounding skin

Treatment is usually only recommended for older children and adults in cases where the spots are particularly unsightly and affect quality of life.

Do not squeeze the spots because it can cause pain, bleeding and an increased risk of spreading the infection. It is also likely to cause scarring.

Read more about treating molluscum contagiosum.

Complications of molluscum contagiosum

MC doesn't usually cause complications and the infection will eventually clear up on its own.

However, in rare cases, the spots can become infected with bacteria. This is more likely to happen if you have atopic eczema (skin irritation caused by an allergy), or if you have a weakened immune system.

If the spots do become infected, you or your child will need treatment with antibiotics.

In rare cases, where spots occur around the eyes, a secondary eye infection may develop, such as conjunctivitis.

Read more about the complications of molluscum contagiosum.

Preventing molluscum contagiosum

Although MC is highly infectious, most people are resistant to the virus and are unlikely to develop MC, even if they come into contact with the virus.

It is therefore not necessary to stay away from work, school or nursery, or to stop doing activities such as swimming.

However, while the risk of passing MC on to others is small, you should take steps to avoid spreading the virus on to people who are not resistant to it.

If you or your child has MC you should:

  • keep affected areas of skin covered with clothing
  • avoid sharing towels, flannels and clothing
  • avoid sharing baths
  • do not scratch the spots because it may lead to other areas of your skin becoming infected and it can prolong the infection

Always use a condom while having sex. However, condoms cannot prevent the spread of the MC virus completely.

The virus can be passed to areas of your skin that are not covered by a condom, such as the areas around your genitals and inner thighs.

Symptoms

Small, dome-shaped, skin coloured papules (spots) are usually the only symptom of molluscum contagiosum (MC).

The spots of MC are firm, raised and usually painless, although they can sometimes be itchy. They are usually 2-5mm wide.

The spots may develop in small clusters and can be spread across different parts of the body.

Some of the spots may have a tiny grey head in the centre and look pearly. If the head ruptures (splits), a thick yellowy-white substance will be released. This substance is highly infectious.

Do not squeeze your or your child's spots. This will increase the risk of the infection spreading to other parts of the body.

In children, spots can develop on the:

  • hands
  • arms
  • face
  • neck
  • chest and stomach

In sexually active adults, the spots usually appear around the:

  • groin area, spreading upwards over the abdomen
  • genitals
  • inner thighs

In rare cases, spots may develop in a number of other places (both in adults and children), including:

  • on the palm of the hand
  • on the soles of the feet
  • inside the mouth
  • around the eyelid

In most cases, otherwise healthy children and adults will have around 20 spots on their body.

Progression

Over a period of about 6-12 weeks, the spots will crust over before eventually healing. The spots do not usually leave scars, but they may leave a small area of lighter skin or a tiny pitted mark.

The molluscum contagiosum virus that causes MC is highly contagious. If the virus spreads to new areas of skin, new spots may develop as the old ones are healing. This can result in an episode of MC lasting for quite a long time, although in most cases the infection clears up after 12-18 months.

Other symptoms

The spots of MC are not usually painful, but you or your child may experience some mild swelling and redness around each spot as it begins to heal.

In about 1 in 10 cases of MC, patches of eczema develop around the spots. Eczema is a skin condition where the skin is red, itchy, dry and cracked. It is thought that this happens because some people are very sensitive to the effects of the MC virus.

Children with atopic eczema (where the skin is particularly sensitive to substances such as dust mites or pollen) are particularly vulnerable to this additional symptom.

Causes

Molluscum contagiosum (MC) is caused by the molluscum contagiosum virus (MCV).

MCV belongs to a family of viruses known as poxviruses, which are particularly well adapted for infecting human skin cells. Smallpox, which was eradicated in the 1970s, also belonged to the poxvirus group.

How the virus is spread

Most people have developed immunity (resistance) to the molluscum contagiosum virus. This means they will not develop MC, even if they come into contact with the virus.

However, people with weak immune systems, such as young children and those with health conditions such as HIV or AIDs, are particularly at risk of infection.

MCV can be spread through:

  • close direct contact – such as touching the skin of an infected person
  • touching contaminated objects – such as towels, flannels, toys and clothes
  • sexual contact – this includes close physical contact as well as full sexual intercourse

If you become infected by the virus and spots appear on your skin, the virus may also spread to other areas of your skin.

As MCV is highly contagious, it can be easily spread among young children at nursery and school while playing and sharing toys.

It is not known exactly how long someone with MC is contagious for, but the contagious period is thought to last up until the last spot has completely healed.

Diagnosis

The papules (spots) of molluscum contagiosum (MC) are usually easy to recognise. Your doctor should be able to diagnose the condition without carrying out further tests.

Your doctor will examine your or your child's skin and they will ask about any other symptoms.

Confirming a diagnosis

If your doctor thinks that you or your child's skin infection may be caused by something other than MC, they may want to carry out some tests.

For example, they may take a sample from one of the spots to test it for the molluscum contagiosum virus (MCV). This is known as a skin biopsy.

If you have spots on your genitals, your doctor may refer you to a genito-urinary medicine (GUM) clinic to be tested for sexually transmitted infections (STIs).

This is because people who develop MC through sexual contact may also have STIs. If you prefer, you can go to an [STI clinic] directly, without an appointment or having to see your doctor. Consultation is confidential and free.

Referral to a specialist

Most cases of MC do not usually need to be referred to a specialist. However, in some circumstances, your doctor may refer you to a specialist. If, for example:

  • you are HIV positive and your symptoms are severe
  • you have a weakened immune system due to other factors, such as receiving chemotherapy
  • you have spots on your eyelids or near your eye, and your eye is red or painful

In most cases, you will be referred to a dermatologist (a specialist in treating skin conditions).

Treatment

Most cases of molluscum contagiosum (MC) clear up without treatment after 12-18 months.

However, MC can take much longer to clear up in people with weakened immune systems, such as those with HIV or AIDs, or those having chemotherapy treatment for cancer. In these circumstances, MC can take up to five years to clear.

Routine treatment is not recommended

A number of treatments are available for MC that can help the infection clear up more quickly. However, routine treatment is not usually recommended, particularly for children. This is because:

  • the infection usually clears up on its own without scarring
  • the infection does not usually cause any symptoms, other than the spots, and it does not usually interfere with daily activities, such as work, swimming, or playing sports
  • treatment can be painful, it can leave scarring, and it may be upsetting for young children

Many doctors and dermatologists will not treat young children with MC if they feel that it would cause the child unnecessary pain and distress.

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

If this applies to you or your child, your doctor may be able to recommend one of the treatments described below.

Topical treatments

There are a number of topical treatments (creams, lotions and ointments) that can be used to treat MC.

All of these treatments were originally designed to treat other types of skin conditions, such as genital warts, acne and psoriasis, but they have since proven effective in treating some cases of MC.

The following topical treatments are usually given under the supervision of a dermatologist (a specialist in treating skin conditions) or another qualified healthcare professional.

Potassium hydroxide

Topical 5% potassium hydroxide is a strong alkali that comes in liquid form. It has recently become available for MC in the UK on prescription or over-the-counter from pharmacists.

Potassium hydroxide works by breaking down the skin cells around the virus, allowing the immune system to respond to it.

The liquid is applied twice a day on each lesion, for around 4-6 days. The lesions should eventually become inflamed, before healing and disappearing within 1-5 weeks.

Side effects of potassium hydroxide can include:

  • hardening and flakiness of the skin
  • swelling of the skin
  • a burning or itching sensation after applying the cream

These side effects are usually mild and often related to the inflammation process necessary to begin the healing process. However, you should contact your doctor if you have side effects that become troublesome.

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 the liquid, which is then dripped onto each spot. You may experience some mild irritation.

Treatment with podophyllotoxin is based on cycles. The first cycle involves applying the medication twice a day for three days. This is followed by four days without treatment. Most people need four or five treatment cycles separated by rest cycles.

Imiquimod

Imiquimod is a cream that may be used to treat larger spots or large clusters of spots. It works by stimulating your immune system into attacking the spots. You apply the cream to the spots before washing it off after 6-10 hours. This should be done three times a week.

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

  • hardening and flakiness of the skin
  • swelling of the skin
  • a burning or itching sensation after applying the cream
  • headache

These side effects are usually mild and should pass within two weeks of stopping treatment with imiquimod.

Benzoyl peroxide

Benzoyl peroxide is usually available in cream or gel form and used either once or twice a day. It should be applied to all parts of your face that are affected by spots, 20 minutes after washing. Use benzoyl peroxide sparingly because too much can harm your skin.

Benzoyl peroxide makes your skin more sensitive to sunlight, so avoid excessive exposure to sunlight and ultra-violet (UV) light, or wear sun cream.

Avoid contact with hair, clothes, towels and bed linen because benzoyl peroxide can bleach these materials. Wash your hands thoroughly after you finish applying the medication.

Common side effects of benzoyl peroxide include:

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

These side effects are usually mild and should resolve after the treatment has finished. However, you should contact your doctor if you have side effects that become troublesome. Your dose may need to be adjusted.

Tretinoin

Tretinoin is available as a gel or cream and is applied once or twice a day to individual lesions. 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 is important to use a reliable method of contraception while taking tretinoin if you are a sexually active woman.

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

Other treatments

The following treatments can be painful, so they are not suitable for children. They must always be carried out by a suitably qualified healthcare professional and should never be attempted at home.

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 will need to wait two to three weeks between each treatment session.

Diathermy

Diathermy uses heat to remove the spots. After you have been given a local anaesthetic to numb the area being treated, your doctor or nurse will use a heated electrical device to burn off the spots.

Curettage

Curettage removes spots by scraping them off with a thin metal instrument called a curette. As with diathermy, you may have a local anaesthetic to numb your skin 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. A bruise is left which should heal within one to two weeks. Most people only need one or two sessions of pulsed-dye laser treatment to clear their spots.

Pulsed-dye laser treatment uses expensive equipment and you are likely to have to pay privately for pulsed-dye laser treatment.

Complications

Molluscum contagiosum (MC) usually clears up on its own without the need for treatment. It rarely causes any other problems.

However, occasionally complications can occur, particularly in people with weakened immune systems. Reasons why someone may have a weakened immune system include:

  • having HIV or AIDs
  • receiving chemotherapy treatment for cancer
  • taking medicines that suppress the immune system (immunosuppressants), such as azathioprine or steroids

People who have had an organ transplant usually need to take immunosuppressants to prevent their body rejecting the donated organ.

Immunosuppressants are also used to treat severe autoimmune conditions, where the immune system attacks healthy tissue by mistake. The digestive condition Crohn’s disease is an autoimmune condition.

The three most common complications that can occur in people with a weakened immune system are:

  • having larger spots than normal – larger than 5mm in diameter
  • having many more spots than normal – in some cases up to 100 spots have been reported
  • having a larger area of the body covered by the spots – such as the chest, face and both arms

Due to the increased risk of developing a more severe form of MC, people with a weakened immune system are usually referred to a dermatologist (skin specialist).

Infection

In some cases, the spots of MC can become infected with bacteria. This is more likely to happen if you have atopic eczema (a skin condition caused by an allergy), or if you have a weakened immune system.

If your or your child’s spots become infected, you will need antibiotics to treat the infection.

Scarring

After MC has healed and cleared, small patches of paler skin or tiny indented scars may be left behind. The scars may be more noticeable if the spots become infected or if you have had treatment for them.

Scarring is more likely to occur in areas of your skin where there is more fatty tissue, such as your thighs.

Eye problems

In rare cases, if you or your child has MC around the eyes, a secondary eye infection may develop, such as conjunctivitis or keratitis.

Conjunctivitis affects the thin layer of skin inside the eyelids called the conjunctiva. It causes your eyes to become red, swollen and watery. You may also have a sticky coating on your eyelids and eyelashes.

Keratitis is similar to conjunctivitis but it affects your cornea (the transparent layer of cells that cover the surface of your eyeball). If you have keratitis, your eyes may be painful and sensitive to light, and you may have blurred vision.

If you or your child develop conjunctivitis or keratitis, your doctor may refer you to an ophthalmologist for specialist treatment. An ophthalmologist is a specialist in diagnosing and treating eye conditions.

Content supplied by NHS Choices