The precise cause of keloid scars is not known. Studies point towards the overproduction of collagen (a protein that is a key component of scar tissue) by cells in the skin known as fibroblasts.

It is possible that keloid scars result from defects with fibroblasts themselves. Alternatively, scars may develop due to changes in the hormones that regulate the activity of fibroblasts. This may explain why keloid scars are more likely to develop during pregnancy or puberty, when the body undergoes significant hormonal changes.

Another theory suggests that the keloid scars develop as part of an immune response to sebum – an oily substance produced by sebaceous glands in the skin.

Keloid scars are characterised by hard and rubbery scar tissue that grows beyond the original borders of a wound. The scars are typically:

• raised above the surface of the skin
• shiny
• hairless
• initially red or purple, becoming brown or pale over time

Keloid scars are usually painless, but they may feel itchy, tender or produce a burning sensation. In the event a keloid scar forms over a joint, movement of that joint may become restricted. The appearance of the scars may also be a source psychological distress.

The sites where keloid scars most commonly develop are the:

• upper chest/sternum
• shoulders
• cheeks
• earlobes

Development of keloid scars

Keloid scars usually develop after some form of injury to the skin. Such injuries include:

• cuts
• scratches
• surgical wounds
• body piercings
• burns
• acne spots
• boils

While keloid scars can develop spontaneously, without prior skin damage, they normally begin to form between 3 and 12 months after an initial injury to skin. They are hard and rubbery in consistency and, to begin with, red or purple in colour. Over time, their colour becomes pale and brown.

Keloid scars typically grow beyond the area of the original injury/wound and continue to slowly enlarge over weeks to months. Some keloid scars may grow over a period of years. Following this period of growth, keloid scars remain the same size or shrink slightly. Unless removed or treated, the scars are usually permanent.

The exact manner in which scars develop will vary from person to person. Most scars grow slowly over time, but in some people, they may enlarge rapidly over a period of months.

Hypertrophic scars

Another form of scar, known as a hypertrophic scar, may also appear after injury to the skin. Similar to keloid scars, they may also appear to be red and raised above the surface of the skin. Hypertrophic scars, however, do not extend beyond the border of the original injury/wound and they also shrink over time, becoming flat and pale.

A GP can diagnose keloid scars from a simple examination of the skin. Further investigations are not usually required.

The GP may ask questions about the initial injury and the extent to which the scars are affecting your life. In the event a keloid scar is near a joint, the GP may want to examine how well you can move that joint.

Keloid scars may get smaller over time, but are often permanent and do not disappear completely. For those worried about the appearance of scars, there are several treatments available. None of the treatments are completely effective and a GP may want to combine treatments.

Steroid injections

Injections of a steroid called triamcinolone have been shown to reduce most keloid scars. The injections are administered every 2 – 6 weeks until there is noticeable improvement. There is a chance that keloid scars will recur with this treatment, causing a need for further steroid injections.

Steroid injections may have side-effects. It is possible for small networks of veins (called telangiectasia) to develop on the surface of the skin at the injection site. The skin may also lose its pigment and become thinner.

Steroid-impregnated tape

Tape that has been impregnated with a steroid (typically fludroxycortide) can also help flatten keloid scars. They are typically applied to the scar for 12 hours per day.

Pressure and occlusive dressings

Applying pressure to scars over long periods of time may reduce the prominence of keloid scars. Special pressure dressings, such as dressing sheets impregnated with silicone gel, are available from your GP. They must be applied to the scar for 12-24 hours a day, for several weeks. In addition to applying pressure, the dressings also prevent the keloid scar from contact with the air.

Other pressure dressings include self-adhesive polyurethane patches. For keloid scars on earlobes, there are special pressure earrings available.

Interferon therapy

Interferon alfa-2b is a type of antiviral medication that may be injected into the keloid scar. The GP may prescribe it in conjunction with steroid injections if steroids alone fail to reduce the size of scars.

Cytotoxic Medications

Cytotoxic medications are drugs that prevent cell division and growth. They are often also used as anti-cancer medication. There are two cytotoxic medications sometimes used for the treatment of keloid scars: bleomycin and 5-fluorouracil. Both come in the form of injections. Cytotoxic drugs may be used alone or in conjunction with other treatments.

Both bleomycin and 5-flurouracil have side effects. Bleomycin may cause darkening and thinning of the skin at the injection site, whereas 5-fluoruracil can cause a loss of skin pigment and pain around the scar.

Retinoids

Retinoids are substances that are similar in chemical structure to Vitamin A. They are often prescribed in the treatment of acne. A GP may consider prescribing a retinoid cream or injection for the treatment of keloid scars. Retinoids do not always produce successful results and, as such, they are not a first line treatment option.

Cryotherapy

Cryotherapy involves freezing the scar using a cold probe or a targeted jet of liquid nitrogen or carbon dioxide. Freezing the scar tissue prevents it from growing larger. As such, cryotherapy is usually used to treat keloid scars in the early stages of development.

The procedure carries of risk of causing the skin around the freezing site to lose pigment and become pale.

Laser Therapy

Laser therapy involves directing high-energy light beams at the keloid scars. The lasers cause the scar tissue to overheat and thus shrink. There are various different types of lasers which can be used: carbon dioxide, argon Nd:YAG and pulsed-dye lasers.

Nd:YAG and pulsed-dye lasers are thought to be the most effective in treating keloid scars, although pulsed-dye lasers may only reduce the redness of scars, rather than their size. Pulsed-dye lasers may also be less effective on dark skin.

Laser therapy can be combined with steroid injections for better results.

Radiotherapy

Radiotherapy involves directing high-energy X-ray radiation at the keloid scars. It is often used after surgery, to prevent scars that have been surgically removed from re-growing. Exposure to radiation can increase the risk of cancer, so the treatment is reserved for scars that are not near internal organs (scars on the abdomen and chest are not suitable for radiotherapy).

Another form of radiotherapy, called brachytherapy, involves inserting small dose or ‘seed’ of radioactive material into the scar. The radioactive material then emits radiation, which destroys the keloid scar. Brachytherapy is also used to prevent keloid scars from re-growing after they have been removed by surgery.

Surgery

Keloid scars may be removed by surgery, but there is a risk that the keloid scar will grow back and to a size larger than before. Careful surgical techniques can minimise this risk, although there may be a need to have other treatments after the keloid scar has been removed e.g. radiotherapy, steroid injections or pressure dressings.

A person may be at increased risk of developing keloid scars if they have:

• Dark skin – Keloid scars are more common in people with dark skin, including those from African, African-Caribbean and South Indian backgrounds. Studies suggest between 6 and 16% of African people develop keloid scars. Another study based in Detroit showed that African-Americans were 7 times more likely to develop keloid scars compared to white Caucasians.

• Previous keloid scars – People with previous keloid scars are more likely to develop another one.

• Family members with keloid scars – About half of people with keloid scars have another family member with the condition.

Keloid scars most commonly develop between the ages of 10 and 30 years. They may also be more likely to occur during puberty and pregnancy.

People at risk of developing keloid scars should avoid unnecessary injury to the skin. This involves avoiding tattoos, skin piercings and any other cosmetic procedures that require the skin to be cut or pierced.

It is also advised to get early treatment for acne, as acne spots can produce keloid scars.

Gauglitz, G. G. (2013). Management of keloids and hypertrophic scars: current and emerging options. Clin Cosmet Investig Dermatol, 6(10).

Keloid. Patient.info – Professional reference article. Available online at: http://patient.info/doctor/keloid-pro

Keloid scars. NHS Choices. Available online at: http://www.nhs.uk/Livewell/skin/Pages/Keloidscarring.aspx

Young, W. G., Worsham, M. J., Joseph, C. L., Divine, G. W., & Jones, L. R. (2014). Incidence of keloid and risk factors following head and neck surgery. JAMA facial plastic surgery, 16(5), 379-380.