Encyclopaedia


Molluscum contagiosum

Introduction

Molluscum contagiosum is a viral skin infection. The most common symptom of MC is small, firm, raised spots on the skin, which usually form in little clusters.

MC is usually painless, although some people may feel mild to moderate itchiness. The condition is not a serious threat to health, but it can be annoying and, in severe cases, it can look ugly.

In most cases, MC will go away within 18 months without the need for treatment.

The condition is highly infectious. However, most people are resistant to the molluscum contagiosum virus, meaning they are unlikely to develop MC if they come into contact with the virus.

At-risk groups

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

  • young children aged one to five years
  • people who have had a number of different sexual partners
  • people with a weakened immune system – either due to a condition such as HIV, or due to complications from treatments such as chemotherapyfor cancer

How molluscum contagiosum is spread

MC can be spread by skin-to-skin contact, or indirectly through contact with objects that have been contaminated by an infected person, such as towels or clothing.

Children often catch it after close physical contact (such as play fighting or hugging) with another infected child.

Adults may catch it after sexual activity.

See Molluscum contagiosum - causes for more information about how the MC virus is spread.

How common is molluscum contagiosum?

It is difficult to know exactly how common MC is in children because the condition is not classed as a notifiable disease. This means that GPs do not have to report cases to the authorities, unlike more serious types of childhood infections, such as measles.

Many adults with MC are also thought to be reluctant to report their symptoms to their GP or local sexual health clinic due to embarrassment because of its association with sexual activity.

Figures from Switzerland and the US suggest that MC is responsible for 1 in every 100 diagnosed skin disorders. It is likely that figures are similar in England.

Outlook

The outlook for children with MC is very good, because the condition is usually mild and gets better by itself without the need for treatment.

The same is true for healthy adults, although some people may decide to have treatment for cosmetic reasons. This is often the case for adults who have a weakened immune system, because they usually develop a more extensive form of the infection.

Treatment for MC usually involves destroying the lesions, which can be done in a number of different ways. See Molluscum contagiosum - treatment for more information.

 

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Symptoms

Small lesions

The most common symptom of molluscum contagiosum (MC) is the appearance of small lesions or abnormal patches on the skin. This is usually the only symptom. The lesions are:

  • firm
  • raised
  • painless

The lesions usually appear in small clusters or are spread widely across different parts of the body. They are usually 2-6mm in diameter. You may notice that some of the lesions have a tiny grey head in the centre and look pearly. This head may rupture (split), causing a thick yellowy-white substance to escape. This substance is highly infectious. You or your child should avoid handling or squeezing the lesions as this can spread the infection to other parts of the body.

In children, the spots of MC can appear on the:

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

In sexually active adults, the lesions usually appear on the:

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

Very rarely, lesions may develop in a number of other places in both adults and children, including:

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

Otherwise healthy children and adults will usually have no more than 20 lesions on their body.

Progression of symptoms

Over a period of approximately 6 to12 weeks, each lesion will crust over spontaneously before eventually healing. The lesions do not usually leave scars, but you may notice that each one leaves a tiny patch of lighter skin or a tiny pitted mark.

As the virus that is responsible for MC can spread to new areas of your skin, you may find that new lesions form as the old ones are healing. This can mean that an episode of MC may last for quite a long time, although in most cases the infection will clear up within 18 months.

Other symptoms

The lesions of molluscum contagiosum are not usually painful but it is normal to have some mild redness and swelling around each lesion as it starts to heal.

However, in about 1 in 10 cases, patches of eczema can develop around the lesions. Eczema is a skin condition where the skin becomes itchy, reddened, dry and cracked. This is thought to happen because some people are particularly sensitive to the effects of the virus that is responsible for MC.

Children who have atopic eczema, which is where the skin is particularly sensitive to substances such as dust mites or pollen, are particularly vulnerable to this additional symptom.

See the Health A-Z topic about Atopic eczema for more information.

 

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Causes

Molluscum contagiosum is caused by a virus known as 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 from the globe in the 1970s, is another member of the group.

How MCV is spread

MCV can be spread through:

  • close direct contact, such as by touching the skin of someone who is infected,
  • sexual contact, this does not necessarily involve full sexual intercourse; it can just be close physical contact
  • sharing contaminated objects, such as towels, flannels, toys, and clothes.

Once you have been exposed to MCV and the skin infection appears, the virus can spread to other areas of your skin.

How infectious is MCV?

MCV is highly infectious, and can be passed easily among children at nursery and school who play together, share toys, and are constantly coming into contact with other children. It is not known exactly how long someone with MCV is contagious, although the contagious period is thought to last up until the last spot completely heals.

However, most people are naturally resistant (immune) to MCV, which means that although they may come into contact with the virus, they will not develop molluscum contagiosum.

People are more likely to be affected by molluscum contagiosum if they have a weakened immune system.  People who are likely to be immunocompromised include those who are receiving chemotherapy for cancer, and those who are HIV positive.

 

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Diagnosis

See your GP if you think that you, or your child, may have the molluscum contagiosum virus (MCV). They will examine your skin (or your child's) and ask about any other symptoms.

Molluscum contagiosum is easy to recognise, so your GP should be able to make a diagnosis based on the appearance of the lesions without needing to do any further tests.

Confirming a diagnosis

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

For example, your GP may take a sample of fluid from the centre of one of the mollusca in order to test it for MCV.

If you, or your child, has one spot that looks different from the rest, your GP may remove it for testing. This is called a skin biopsy.

If you have molluscum contagiosum on your genitals, your GP may refer you to a genito-urinary medicine (GUM) clinic to be tested for other sexually transmitted infections (STIs). This is because people who have developed MC through sexual contact may also have contracted other more serious STIs. If you prefer, you can attend an STI clinic directly, without an appointment or seeing your GP. Consultation is confidential and free.

Referral to a specialist

In most cases of molluscum contagiosum, referral to a specialist is not usually necessary. However, in some circumstances, your GP may refer you to a specialist. For example, you may be referred to a specialist:

  • If you are HIV positive and your symptoms are severe.
  • If you have lesions on your eyelid or eye, and your eye is red.
  • if there are other factors, apart from an HIV infection, that mean you have a weakened immune system – for example, you may be having chemotherapy for cancer

In most cases, referral to a dermatologist will be recommended. A dermatologist is a specialist in treating skin conditions.

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Treatment

In most cases, molluscum contagiosum (MC) will clear up and heal within 18 months without any treatment.

However, MC can take longer to clear up in people who have a weakened immune system, such as those receiving chemotherapy for cancer or those who are HIV positive. In these circumstances, MC can take up to five years to clear.

Why routine treatment is not recommended

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

  • the infection usually clears up on its own without any scarring
  • the infection does not usually cause any symptoms (other than the lesions) and does not usually interfere with everyday activities
  • treatment can be painful and cause scarring, which may upset and distress young children

Thus many GPs and dermatologists refuse to treat young children when there is no clinical need, because they feel that it would cause the child unnecessary pain.

Treatment is only usually recommended for adults and older children when the spots of MC are particularly ugly and are affecting the person’s quality of life. If this applies to you or your child, contact your GP as they can recommend one of the treatments outlined below.

Squeezing the lesions

Squeezing the lesions is the first and the simplest type of treatment for MC. The aim of squeezing the lesions is to remove the pearly grey core at their centre. This is the part that contains the molluscum contagiosum virus (MCV).

Do not try to squeeze the lesions before consulting your GP. If they advise you to squeeze the lesions, wash and dry your hands thoroughly both before and afterwards. After drying your hands on a towel, wash the towel immediately on the hot cycle of your washing machine.

If you do not follow these important hygienic precautions, the lesions may become infected by bacteria that are already present on your skin. Your GP can advise you about whether your child should have their spots squeezed or whether it is better to let the infection clear by itself.

Your GP can squeeze your or your child’s lesions, or they can train you to safely squeeze the lesions yourself. Your GP may use a small pair of forceps or tweezers to squeeze the lesions, but you may find it easier to use your fingers.

If you want to remove the cores of the lesions yourself, do it after you or your child has had a bath, as the skin will be softer. Wear disposable gloves, wash your hands before and afterwards, and carefully dispose of the contents of the lesions. If you use a pair of tweezers, remember to sterilise them afterwards using antiseptic solution.

An alternative to using tweezers is to use a wooden toothpick to tease out the core of the lesion. Afterwards, put the toothpick in the dustbin.

Removing the cores of the lesions can be painful, so it may be best to treat a small number at a time. Once the lesions have been treated and their contents removed, they are likely to heal within one to four weeks.

Other procedures

If removing the cores of the lesions does not work, other types of treatment can be used for MC. The following treatments can be painful, so they are not suitable for children. They must always be carried out by a healthcare professional and should never be attempted at home.

Cryotherapy

Cryotherapy involves freezing the lesions with liquid nitrogen to remove them. Each lesion 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 lesions. After you have been given a local anaesthetic to numb the area being treated, your GP or nurse will use a heated electrical device to burn off the lesions.

Curettage

Curettage removes lesions 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.

Topical treatment

A number of topical treatments (creams, lotions and ointments) are sometimes used to treat cases of MC. All of these treatments were originally designed to treat other types of skin conditions, such asgenital 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 or another qualified healthcare professional, rather than your GP.

Podophyllotoxin

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

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

Imiquimod

Imiquimod is a cream that is usually recommended to treat larger lesions or large clusters of lesions. Imiquimod works by stimulating your immune system into attacking the lesions. You apply the cream to the lesions, then wash it off after 6-10 hours. This should be done three times a week.

It can often 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 lesions, 20 minutes after washing. Use benzoyl peroxide sparingly as 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

The side effects are usually mild and should resolve after the treatment has finished. However, you should contact your GP if your side effects become troublesome as your dose may need to be adjusted.

Tretinoin

Tretinoin is available in gel or cream form 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 can take several months of treatment with tretinoin before you notice an improvement in your symptoms.

Pulsed-dye lasers

A relatively new type of treatment for MC is pulsed-dye laser treatment. This involves using a powerful beam of light to destroy the cells that make up each individual lesion. Afterwards, a bruise is left. It should heal within one to two weeks. Most people only need one or two sessions of pulsed-dye laser treatment to clear their lesions.

One practical disadvantage of pulsed-dye laser treatment is that it involves using expensive equipment. Availability is therefore limited on the NHS. Priority will be given to people who have more severe skin conditions, such as disfiguring birthmarks.

You are likely to have to pay privately for pulsed-dye laser treatment. The cost of treatment will depend on how many shots of the laser are required. An average session usually costs around £100-£200.

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Complications

Molluscum contagiosum usually clears without the need for treatment, and it rarely causes any other problems.

However, complications can sometimes occur, particularly in people who have weakened immune systems. For example, the mollusca may be larger, there may be more of them, and they may be more widespread across your body.

People with weakened immune systems include those who are:

  • Receiving chemotherapy.
  • HIV positive.
  • Taking medicines that suppress the immune system (immunosuppressants), such as azathioprine or steroids

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

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

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

  • having larger lesions than normal – larger than 6mm in diameter
  • having many more lesions than normal – in some cases, up to 100 lesions have been reported
  • having a larger area of the body covered by the lesions, 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 lesions that are caused by molluscum contagiosum can become infected with bacteria. This is more likely to occur if you have atopic eczema (skin irritation caused by an allergy), or if you have a weakened immune system.

If your or your child’s mollusca become infected, treatment with antibiotics will be needed in order to fight the infection.

Scarring

Once molluscum contagiosum 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 mollusca become infected, or if you have had some form of 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 molluscum contagiosum around your eyes, you may develop a secondary eye infection, such as conjunctivitis or keratitis.

Conjunctivitis affects the thin layer of skin inside your 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 eyes). If you have keratitis, your eyes may be painful and sensitive to light, and your vision may be blurred.

If you or your child develop conjunctivitis or keratitis alongside molluscum contagiosum, your GP may refer you (or them) to an ophthalmologist (an eye specialist) for specialist treatment.

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Prevention

Molluscum contagiosum is highly infectious. However, most people are resistant to the molluscum contagiosum virus (MCV).

This means that even if you, or your child, come into contact with MCV you will be unlikely to develop molluscum contagiosum. For this reason, if either you, or they, have molluscum contagiosum, it is not necessary to stay home from work, school, or nursery or stop activities such as swimming.

However, while the risk of passing molluscum contagiosum on to others is small, it is sensible to try to avoid spreading MCV as much as possible. Therefore, if you or your child has molluscum contagiosum you should:

  • keep affected areas of skin covered with clothing, where possible,
  • avoid sharing towels, flannels, and clothing with others,
  • avoid sharing baths, and
  • avoid scratching the spots (mollusca) if they are itchy because this can cause MCV to infect other areas of your skin and prolong the infection.

If you or your child have particularly troublesome symptoms of itchiness, contact your GP. They should be able to give you a mild steroid cream that can improve symptoms.

Lesions on the genitals

If you have lesions on your genitals, you should also be screened for other possible sexually transmitted infections (STIs) at a genito-urinary medicine (GUM) clinic.

You should always use a condom for sexual intercourse. However, it is important to remember that condoms cannot prevent the spread of MCV completely. It is possible for the virus to be passed to areas of your skin that are not covered by a condom, such as the area around your genitals and your inner thighs.

 

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Selected links

Atopic eczema

Conjunctivitis

 

 

 

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The information on this page has been adapted by NHS Wales from original content supplied by NHS Choices.

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