Keloid on elbow

Keloid Definition, Causes, Treatment, Are You At Risk?


What Is A Keloid?

The cornerstone of the skin’s healing process is the production of collagen. Collagen can be thought of as the “glue” the human body creates to mend wounded skin. It is the amount of collagen laid down in the wound, as well as its color, texture, and other features that determine what a particular scar will look like. A minimal amount of skin-toned collagen is ideal and produces a scar that is fine, flat, and blends into the surrounding skin. Too much collagen, and a problematic keloid scar that is raised, wide, and discolored can be the result. Keloid scars can also be persistently itchy and painful and are a source of both physical and emotional stress.

Normal scar
A normal scar has minimal collagen content so it’s flat and generally subtle.
Image of three variations of keloid scars
Keloids like these have excessive amounts of collagen that have been deposited at the wound site.

What Causes Keloids?

Any break in the skin can cause a keloid scar in a prone individual. Injury, surgery, piercings, tattoos, and even skin conditions like acne can provoke these highly problematic scars in high-risk people. It is also well established that some keloids seem to appear spontaneously without any known cause. It is likely that in these cases, the keloid came from very minor trauma to the skin such as an insect bite or ingrown hair. The glaring point is that in high-risk individuals, even the most minor skin injuries, that would lead to little or no scarring in non-prone individuals, can create keloid scarring in those that are predisposed.

image of hyoertrophic acne scars on the face
Keloid scars cane be caused by acne.

Keloids Risk Factors:

As noted, keloids are the result of an extreme excess of collagen being deposited by the body to heal a wound. The healing process, and associated scar tissue formation, basically gets stuck with the scarring switch in the “on” position. Why keloids form in certain individuals but not in others is not fully understood. But, a number of risk factor and protective factors have been identified that increase or decrease a person’s chances of getting a keloid:

Wound Healing Complications

Slower wound healing has been shown to increase the risk of keloid scarring. Delayed healing leads to an increase in the volume of collagen that the body deposits at the wound edges. Essentially any adverse event or complication that slows healing can increase the risk of poor scarring. Wounds that become infected, that experience disruption of sutures and open prior to full healing, or piercings that become infected heal slower and are prone to heavier scar formation.

An open wound like this one that will be slow to heal is at higher risk for a keloid scar.

Body Area & Keloid Scars

Body area is at the top of the list of factors that influence scar quality. Amongst the most common sites for keloids to form are: the chest, upper limb, shoulder, upper back, middle of chest over the breastbone, lower abdomen, upper pubis, and ear. Factors such as increased skin thickness (eg. back, shoulder, cheeks versus eyelids and genitalia), high concentration of oil glands (ear and neck), and increased pigmentation (face versus palm of hand) have been shown to correlate with increased keloid scar risk.

Keloid scarrinng of the shoulder and ear
Some body areas, including the shoulder and ear, are at increased risk for keloid scarring.

Your Existing Scars

Experts in the field of wound healing and scarring widely agree that the single most important factor in predicting a person’s healing tendencies is the quality of the scars that person already has. This is because existing scars are the living proof of how the many complex factors that make up an individual’s natural scarring tendencies come together and interact to create scars of a particular quality. A history of poor scarring overrides all other factors when anticipating an individual’s future scar quality.

Complications Matter

If significant adverse events or complications, such as infection or wound opening occurred during the healing that can be confidently said to have negatively affected the quality of the final scar, the predictive value of that scar with respect to future scarring will be much less. It would remain highly possible that future scars could be of high quality assuming that they healed smoothly and without similar complications. Conversely, a poor scar that emerged from what can generally be described as a smooth and uncomplicated healing process provides a stern warning that future scarring will likely be unsatisfactory as well.

Keloids and other types of scars
Different types of scars could be indicative of future scar quality for these individuals.

Ethnicity & Keloid Scarring

There is a well-documented increase in the incidence of keloids in Blacks, Latinos, and Asians. Black individuals may be as much as 15 times more at risk for keloids than Caucasians and are also predisposed to developing keloids that are larger in size. Individuals of Native American, Hawaiian/Pacific Islander, and Middle Eastern descent are also at moderately increased risk for keloids compared to Caucasians who, statistically, are least at risk.

Ethnicities including African-Americans have been well-documented to have variable risks for keloid scars.

Skin Tone

There is a clear relationship between the extent of pigmentation of a person’s skin and the risk of keloid formation. Darker-skin individuals are at higher risk – potentially up to 15 times greater than those with fairer skin. Studies have shown that as natural skin tone increases from white to dark black, so does heavy scarring risk. Interestingly, this trend applies to an individual person as well in that body areas showing maximal pigmentation such as the face are known to be at higher risk for heavy scarring than those less pigmented body areas such as the palm of the hands and soles of the feet. The reason behind this is not fully understood, but it is believed that the skin pigment molecule known as melanin stimulates collagen production during healing to promote thicker, heavier scar tissue.

People with darker skin tones have a higher risk for making keloids than lighter-toned individuals.

Age & Keloid Scars

Keloids occur most frequently between the ages of 10 to 30 years old. Children less than 10 years of age rarely form keloids, and in adults, the incidence of keloid scars decreases progressively as age increases above 30 years. Puberty-related hormones such as testosterone and estrogen are likely the culprit, with the surge in these hormones that occurs at puberty playing a key role in keloid formation. Some researchers believe that keloid formation may be higher in the 10-30 years age group simply because it is a time in life when individuals are more prone to injuries due to more frequently engaging in riskier activities.

Young people keloid more often than older people, possibly because of being involved in higher risk activities.

Family History

An important factor in predicting an individual’s keloid risk is a positive family history. Positive family history for keloids can suggest that:

  • you may have up to 10 times greater risk of keloid scarring as well especially if a family member developed a keloid scar on the same body area that your wound is
  • you may be prone to forming keloids that are larger in size
Genetics play a role in keloid scars
Amongst all scar types, keloids are the most dependent on genetics and family history.

High Blood Pressure

High blood pressure (hypertension) has been found to associated with an increased risk for keloid scar formation. This may be because the condition causes damage to blood vessels which, in turn, increases tissue inflammation during healing. The strength of this association is likely only moderately significant. It is unclear if lowering blood pressure through lifestyle and dietary changes or prescription medications eliminates the increased risk for keloids. Long-standing hypertension has also been correlated with the increase in size of keloids.

A relatively minor and overlooked risk factor for keloid scarring is high blood pressure.

Nicotine Use

Ironically, cigarette smoking has been shown through clinical research to be protective against the formation of keloids. A leading theory is that the decrease in blood flow to skin associated with nicotine leads to decreased inflammation at the site of the wound.  This by no means suggests that it is wise to smoke cigarettes around the time of surgery or any other time skin is healing! The adverse effects of cigarette smoking on general health, and even to other aspects of wound healing far outweigh the benefit of nicotine with respect to decreasing rates of keloids.

Nicotine can decrease keloid risk, possibly by inhibiting collagen production.

Pregnancy & Keloid Scarring

Pregnant women are at a somewhat greater risk to develop keloids compared to the general population. There is likely a hormonal explanation for this phenomenon. The hormonal shifts, particularly elevated estrogen, that occur during pregnancy, increases the incidence of keloid formation.  Some research shows that keloid scars, especially of the ear, that have been previously treated successfully can recur during pregnancy. It is also possible that this effect may then reverse itself after pregnancy.

Pregnant women have a greater risk for keloids.

Asthma, Eczema and Allergies & Keloids

Asthma, eczema, and allergies have been correlated with an increased risk of keloid scar formation. These conditions are associated with elevated levels of specific biological agents which contribute to inflammatory responses that can provoke the excessive collagen deposition associated with keloid scars. Keloid risk may be more than three times higher in individuals with a diagnosis of eczema. Keloid-formers may also be up to five times as likely to have a history of asthma as non-keloid-formers. It has not been clearly shown that controlling one’s allergies, asthma, or eczema by the use of medications eliminates or decreases the increased risk of heavy scarring associated with these conditions.

Inflammation associated with asthma and allergies may also be involved with an increased risk for keloids.

Keloids & Blood Type

Blood type A appears to be a risk factor for the formation of keloid scars. One study has shown up to a 3 to 4 times increase in keloid risk for blood type A individuals over those with blood types B, AB, and O. The cause for this has not been completely worked out but is likely related to inflammation during the healing process that is stimulated by the structural elements found on the red blood cells of type A blood.

Image showing blood types relationship to keloid scar risk
Keloid risk is higher with blood type A.

Body Mass Index & Keloids

A person’s body type is often defined using a calculation called the body mass index (BMI). The BMI relates an individual’s weight to their height. Studies have repeatedly shown an increased risk for keloid formation in individuals with a higher BMI. Theories for why this so include that fat tissue stores biological agents that increase inflammation during wound healing. Moreover, obesity is thought to have deleterious effects on skin circulation which can also negatively impact scarring.  The association between keloid formation and a higher BMI has been shown in at least one study to be most relevant for keloids occurring on the ears more than other body areas. 

Greater BMI carries higher keloid scarring risk.

Keloid Scarring & Medications

Emerging evidence exists that patients who are taking a class of medications known as ACE-Inhibitors (angiotensin-converting enzyme inhibitors) have a significantly lower risk for forming keloids and hypertrophic scars when compared to patients not taking these medications. Commonly prescribed ACE inhibitors include: 

  • Prinivil/Zestril otensin 
  • Monopril 
  • Altace 
  • Accupril 
  • Aceon 
  • Mavik 
  • Univasc 

There is also evidence that a class of drugs known as statins, used to lower cholesterol levels, may be effective in reducing scarring. Commonly prescribed statins include:Lipitor

  • Lescol
  • Mevacor
  • Pravachol
  • Crestor

These medications are not currently being prescribed by physicians to prevent or treat heavy scarring. However, individuals already taking one or more of these drugs may harbor some protection against keloid scarring according to recent medical research.

Some medications decrease keloid risk.

Kleoids & Skin Tension

When a wound is stitched or stapled closed after injury or surgery, one of the most critical technical factors that contribute to scar quality is the tension (tightness) on the wound after it is closed. It is believed that increased tension on a closed wound provokes an inflammatory reaction at the wound edges that can cause heavier, thicker scarring. Excisions of larger growths, like a large mole or surgeries such as tummy tuck which are intentionally stitched tight, are at increased risk for keloids compared to wounds that are stitched with the skin in a more relaxed state. Overcoming tension on wound closure is a critical element of the surgical procedure and is achieved by the use of multiple layers of sutures and post-operative wound support with taping.

Excision of a large mole like this one may be prone to keloid formation because the closure with stitches will be under considerable tension (tightness).

Practitioner Skill & Technique

Regardless of a person’s natural healing tendencies, procedural technique always plays a critical role when it comes to scar quality. That said, under the right circumstances, a person’s combined risk factors can also overcome any practitioner’s ability to produce results with fine, aesthetically excellent scars. For instance, a patient with a strong family history for keloids having a procedure done on a high-risk area of the body may form a keloid in spite of even the most meticulous, careful, and skilled techniques and after-care. In that light, a surgeon, tattoo artist, or piercer can heavily influence, but not determine, the scar quality her or his client achieves. Put another way, excellent technique can help to minimize but not eliminate the chances of poor scarring. 

Surgical technique can play a role in keloid scar risk
Practitioners can influence but not guarantee final scar quality.

How To Prevent Keloids:

You can get a much better handle on your personal keloid risk by using the ScarScore Scar Calculator. Keloids are notoriously hard to treat and have a very significant rate of recurrence. Avoiding a keloid altogether is the best bet. If you’re set on having that elective surgery, piercing, or tattoo, or if you’ve sustained an injury, here are some keloid-prevention measures to be aware of:

follow all after-care instructions carefullycomplications increase keloid risk
prolonged use of silicone gel or silicone strips for 6 monthsproven to help prevent thicker scars with prolonged use
compression earrings after ear-piercing for 6-12 monthscan softens and flatten scars
cortisone injectionsa mainstay of keloid scar prevention
Botox injectionsreducing muscle tension can help prevent keloid scarring
5-FU, verapamil, and bleomycin all have been shown to help avoid keloids

How To Get Rid Of Keloids:

If you already have a keloid scar, there are measures that can be taken to improve it. The biggest challenge with keloids is recurrence. Someone who made a keloid scar from a surgery, piercing, tattoo, or injury, is by definition prone to keloids. The dilemma is if you’re prone to keloids, you’re also at high risk to make a keloid from any procedure, such as surgery, that removes the keloid. The situation can, indeed, become a vicious cycle. That said, keloid treatment can also be very worthwhile. Results can vary from minimal to no improvement (in some cases treatments can make the keloid worse) up to excellent improvement. Everything in between is possible too, with many treatments resulting in some degree, but incomplete, recurrence of the keloid scar.

For existing keloids, existing treatments include:

use of silicone gel or silicone strips for as long as improvement is occurringproven to improve even scars that have been present for years
cortisone injectionssoftens and flatten scars
cryotherapy (freezing)a relatively new and promising treatment
5-FU, verapamil, and bleomycin injections help improve keloid scarring
Botox injections (botulinum type A toxin)decreasing muscle tension can help improve thick scarring
lasersoftens scars and reduces discoloration
surgical scar revision if still problematic at 1 year, followed by aggressive preventative measuresremoves scar completely; goal becomes preventing recurrence
radiationpowerful modality, usually used after surgery, many potential side effects
so used only in severe cases


An extremely complex brew of genetic and lifestyle factors interact to determine any individual’s overall risk for keloids. Additionally, the skill and technique of your chosen practitioner will always play a role. A smooth, complication-free healing process is also critical to minimize keloid scarring risk. Because of the devastating physical and emotional impacts that keloids have, understanding your own risk is critical prior to undertaking surgery, piercings, and tattoos and after an injury. To learn more about the prevention and treatment of keloid scars, have a look at our article on the topic.

The content (text, graphics, images, and all other materials) provided throughout this website is informational in nature only and does not constitute medical advice. The content provided on this website is not intended as a substitute for professional medical advice. Any questions you have regarding any medical condition, treatment, intervention, pharmaceutical, vitamin, supplement, or other should be addressed with a qualified healthcare practitioner. ScarScore Inc. makes no guarantees whatsoever on the safety or efficacy of any of the treatments, products, or other medical interventions described on this website. Health conditions and drug information contained in the content of this website are subject to change and are not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. ScarScore Inc. does not endorse any test, healthcare practitioner, product, procedure, opinion, service, or other information that is described in the content of this website.