Molluscum contagiosum is a viral skin infection which commonly appears in children and immunocompromised individuals. These round bumps appearing on the skin are generally harmless and will disappear in 6 months to 2 years if left untreated. However, irritation around the bumps could lead to infections, so a range of treatments have been developed to remove them.¹ Cryotherapy, the process of using extreme cold to destroy tissue, is a commonly used method to treat Molluscum contagiosum.² In this article, we will discuss the benefits and limitations of the treatment, as well as its practical application and relative efficiency to other treatments.

About Molluscum contagiosum

Molluscum contagiosum is caused by a virus of the Poxviridae family, which is transmitted by direct contact with infected skin. For this reason, it is common in sexually active individuals, but it can also spread through contact with infected objects.^1,3 A compromised immune system can also facilitate infection, as the body’s ability to fight the virus is weakened. This can occur through conditions such as HIV or if the patient is undergoing chemotherapy. Also, individuals with atopic dermatitis are prone to infection by Molluscum contagiosum virus (MCV), as the rashes that are common with the condition serve as entry points for the virus.³

Individuals with MCV develop bumps on the skin, which can occur anywhere but are mostly concentrated around the trunk and genitals. The disease is self-limited, which means that it will resolve itself without any treatment. The bumps are harmless, but skin irritation can lead to infection, so treatment to remove them is recommended. Common ways of treating Molluscum contagiosum include topical therapies, physical removal of the bumps and cryotherapy.

Cryotherapy: mechanism and efficacy

Cryotherapy is a technique that involves the application of extreme cold to the intended tissues, which causes widespread cell death. This is due to the formation of small ice crystals inside the cells, which leads to the rupture of the cell membrane. In Molluscum contagiosum, the individual bumps are exposed to extremely cold substances, such as liquid nitrogen, which then causes the aforementioned effects. In situations like Molluscum contagiosum, where only the surface of the skin is treated, the therapy is usually delivered via a concentrated spray or applied with a cotton swab. Each lesion is treated independently for 5-10 seconds, and depending on the number or size of the lesions, multiple sessions of cryotherapy may be required.^3,4

Cryotherapy has been extensively studied for treating Molluscum contagiosum, consistently showing clearance rates of between 70 and 90%.⁵ However, the effectiveness of the treatment is not always consistent, as more predisposed patients (e.g. immunocompromised patients) may not show the same positive results as others and may require additional sessions to completely rid them of their lesions.¹

Benefits and drawbacks of cryotherapy

Cryotherapy as a treatment option for Molluscum contagiosum offers a range of benefits that make it an attractive choice. Firstly, it has a high degree of effectiveness and can remove the lesions reliably and safely. It is a quick treatment, and the lesions may be completely removed after a few sessions, which could be beneficial for those patients concerned with the aesthetic aspect of the disease. It is not an invasive treatment, making it simple and less prone to complications that could arise from surgical options. It is an accessible option and does not require any complicated equipment or specialised facilities.^1,4 This means it can be used to treat patients who don’t have access to medical centres or live in areas that lack medical infrastructure. 

However, cryotherapy is not without its downsides, which could limit the extent to which it can be used to treat Molluscum contagiosum. The application of extreme cold, while only for a few seconds, can be uncomfortable and painful. With the majority of patients being children, most between the ages of 2 and 5, this can be especially distressing for them and discourages their use. Hypopigmentation is also a noted side effect of cryotherapy, where the area of treated skin can take on a lighter tone than the skin around it. 

Cryotherapy also often causes blistering in the treated area. This usually scabs over and heals within 2-4 weeks, but it does mean the patient is exposed to secondary bacterial infections.³ With many of the individuals suffering from Molluscum contagiosum being immunocompromised, this risk may invalidate the treatment and make patients consider alternative options. Finally, the effectiveness of cryotherapy often varies with the skill of the practitioner and the nature of the lesions. Bigger or inconveniently located lesions may be more resistant to treatment, requiring more sessions to remove them completely. 

How does cryotherapy compare to other treatments?

Cryotherapy has been proven to be one of the most effective treatments for Molluscum contagiosum, but other treatment options should not be ignored, as patients may not be eligible or be averse to cryotherapy. 

Topical treatments 

Topical agents can be very effective in managing Molluscum contagiosum. Compounds such as cantharidin or salicylic acid have been used, and while effectively removing lesions, they can cause irritation of the skin and they often have to be used for longer than a cryotherapy regimen.

Curettage 

Bumps can be physically removed by a practitioner using a device called a curette. If properly done, there will be little or no bleeding, but it can be distressing for children, and is normally only done in older patients.³

Laser treatments 

Different types of lasers can be used to remove bumps caused by Molluscum contagiosum, such as a CO₂ laser or a pulsed dye laser. After treatment, the skin will take 2-4 weeks to heal completely, and it is a very effective method of treatment. However, it requires specific equipment and facilities, making it less accessible and less widely used than other methods, such as cryotherapy

Practical considerations and patient selection

There are a number of limitations and practical aspects that must be considered when deciding if cryotherapy is the right treatment option. Firstly, patient age is important, as children often handle the pain and burning sensations associated with the treatment worse than older patients; a local anaesthetic or an alternative option may be recommended. 

The location of the lesions can also play a vital role in the application of cryotherapy. For example, in patients where the disease has been sexually transmitted, the lesions are often seen around the genitals, and cryotherapy in these cases needs to be tailored to the specific needs of the patient. 

Summary

Molluscum contagiosum is a self-limited skin condition that comes about via viral infection and is spread by direct contact with infected skin. Because of this, it is often spread in sexually active individuals, but can also be contracted through contact with an infected surface, and is commonly associated with the use of public swimming pools. It mainly affects sexually active people, children and immunocompromised individuals, and manifests as harmless bumps that can appear anywhere, but focus mostly around the trunk and genitals. Without treatment, these will disappear anywhere from 6 months to 2 years, but aesthetic or infection concerns usually mean people seek treatment to remove them.

Cryotherapy is a common and effective treatment for Molluscum contagiosum. It delivers quick and effective results and is minimally invasive, but it can be painful due to the extreme cold, making some patients seek alternative options. These include topical treatments and physical removal of the bumps, either by removing them with a curette or a laser. Cryotherapy is also associated with hypopigmentation, where the treated skin will become a lighter tone than the skin around it, which could limit its use in some patients. However, ease of application and accessibility make it a very cost-effective option, and very suitable for people with limited access to healthcare or more complicated treatments.