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What are the side effects of laser hair removal? Dr Emily Altman

Posted Oct 03 2011 6:28am

Today, laser hair removal (LHR) is the most commonly requested cosmetic procedure in the world and is routinely performed by dermatologists, other physicians, and non-physician personnel with variable results.  Although it is seemingly a simple cosmetic procedure, it does carry a risk of side effects and complications.  The number of laser hair removal side effects goes up when LHR is performed by non-physician supervised providers (1,2).

The Food and Drug Administration allows for all devices on the market today to be labeled “for permanent hair reduction” because with LHR the hair follicles are not destroyed, and the hair has a potential to grow again under certain circumstances.

For the physician, a number of factors go into achieving optimal LHR results while minimizing complications and side effects for his/her patients:

  • Knowledge of hair follicle anatomy and physiology
  • Proper patient selection and preoperative preparation
  • Adherence to principles of laser safety
  • Familiarity with the various laser/light devices
  • A thorough understanding of laser–tissue interactions.

Because the process is complicated and involves medical decision-making, the risk of potentially permanent adverse effects goes up significantly when LHR is performed by non-medical, non-physician-supervised or poorly trained personnel.

To understand the potential problems with LHR, let’s look at some anatomy first.

Hair types

There are three main types of hair:

  • Lanugo hair is fine hair that covers the fetus and are shed in utero at about 36 weeks gestation.
  • Vellus hair is short, fine, light-colored, and barely noticeable hair that develops on most of a person’s body from his/her childhood.  Exceptions include the lips, the back of the ear, palms, soles, some external genital areas and the navel.  Vellus hair cannot be removed by LHR due to lack of pigment.
  • Terminal hairs are thick, long, and dark, as compared with vellus hair.  During puberty, the increase in androgenic hormone levels causes vellus hair to be replaced with terminal hair in certain parts of the human body.
vellus vs terminal hairs

The parts of the body that grow terminal hair will have different levels of sensitivity to androgens, primarily of the testosterone family.  The pubic area and underarms are particularly sensitive to such hormones.  Development of pubic and axillary hair on both men and women is considered a secondary sexual characteristic, although men will develop terminal hair in more areas. This includes hair on the face, chest, abdomen, legs, arms and feet.

Women retain more of the vellus hair, unless a hormonal abnormality exists. For example, women with polycystic ovary syndrome (PCOS) have an excess of androgens, which causes them to grow terminal hair in predominantly male areas.

Vellus to terminal hair transition


Hair color

Hair color is determined by the amount of pigment in the hair shaft.  Melanocytes, pigment-producing cells in the skin and hair follicles, make two types of melanin:

  • Eumelanin – a brown-black pigment
  • Pheomelanin – a red pigment.  Hair that predominantly has eumelanin cannot be effectively treated with LHR.

Definitions of excess hair

The definition of excessive or unwanted body hair varies by cultural standards.  What may be unwanted hair in one society may be perfectly normal in another.  Excessive hair can be classified as:

  • Hypertrichosis – a localized or generalized growth of excess hair at any body site that is not androgen-dependent.
  • Hirsutism – abnormal growth of terminal hair in women in androgen-dependent sites, such as the face and chest.

How does laser hair removal work?

Laser hair reduction works by selectively targeting the pigmented hair follicle by using melanin as a chromophore (a substance that absorbs light).  Melanin then absorbs the heat delivered by the laser and transfers it to the nearby growth control center of the hair follicle (stem cells).  An excellent review of hair follicle structure and  can be found at .

Hair follicle

Hair follicle with a terminal hair and sebaceous (oil) gland. The stem cell area (the bulge) is located somewhere near the undersurface of the sebaceous gland

Heating of the stem cell area causes the hair to become lighter and finer until it is small and fine enough not to be seen above the skin surface. The hair is not actually destroyed, nor is the hair follicle scarred.

The ideal candidate for LHR is fair skinned with dark terminal hair.  This allows for maximum efficacy of the LHR procedure, since the lasers target the significantly larger amount of melanin in the hair follicle and can practically ignore the small amount of melanin in the epidermis, the surface of the skin.  However, due to the development of new laser devices and technologies that can protect the epidermis while treating the hair, LHR can today be successfully performed in all skin types.

Although in many patients, laser hair reduction can be achieved for prolonged periods of time, sometimes even permanently, under certain conditions, like hormonal changes during menopause or in women with polycystic ovary syndrome, the treated hair follicles can get activated again and start producing dark terminal hairs that again grow above the skin surface (4).

Laser hair removal side effects

Because the laser preferentially targets the darker areas, the major potential side effect is burning the epidermis (surface layer of the skin), since it also contains melanin. That can result in darkening (hyperpigmentation) or lightening (hypopigmentation) of the skin. If the burn goes beyond the epidermis into the lower layers of the skin, blistering, ulceration, bruising and actual scarring and skin texture change can result.

It is extremely important to make sure that laser hair removal is not performed on anyone who has had sun exposure to the area to be treated within at least six weeks before laser hair removal. When the skin tans, the melanin darkens and the difference between the skin and hair color is significantly reduced. That makes it more likely that the laser will hit the pigment in the epidermis and cause a burn.  Sun exposure should be avoided for six weeks after LHR as well, due to the risk of hyperpigmentation of treated areas.

It is also important to carefully and accurately determine the person’s skin type prior to the procedure. That is done by means of a detailed questionnaire, and not by just glancing at the skin and making a judgment. Skin type determines the proper settings on the laser that will also minimize the potential for side effects.

Because there is a large number of  medications can make the skin light-sensitive, laser procedures should be held until the patient can safely discontinue the medication, as increased sensitivity to light can result in burns from LHR.  Common medications like antibiotics, diuretics, over-the-counter supplements, such as St John’s Wart and others can make the skin light-sensitive.  A history of any gold intake is a contraindication for laser therapy.

Other potential side effects of laser hair removal are hive-like reaction, infection, acne flare-ups and folliculitis.  There is also a low risk of paradoxical hypertrichosis (an increase in hair growth) in type IV or greater skin patients of Mediterranean, Middle Eastern or Asian descent, especially on the face.

We have body hair for a number of evolutionarily important reasons. Ultimately the desire to keep or remove hair is determined by the individual. The great thing about laser hair reduction is that, should a person choose to remove the hair, it can give excellent, long-lasting results. All the other available hair removal methods, like shaving, waxing or using depilatories, are temporary and may have their own side effects.

To decrease the risk of side effects, it is best to have the procedure done by a board-certified, trained and experienced physician, to do careful skin typing and to avoid sun exposure for at least six weeks prior to and after treatment.


  1. Vano-Galvan S, et al. Complications of nonphysician-supervised laser hair removal: Case report and literature review. Canadian Family Physician. 2009;55:50
  2. Haedersdal M. Potential risks of non-physicians’ use of lasers and intense pulsed light in dermatology [in Danish] Ugeskr Laeger. 2005;167(43):4095–7
  3. Ibrahimi OA et al. Laser Hair Removal. Dermatol Ther. 2011 Jan-Feb;24(1):94-107
  4. Brodell LA, Mercurio MG. Hirsutism:  Diagnosis and Management. Gend Med. 2010 Apr;7(2):79-87.
  5. Goldberg D. Laser Complications: Hair Removal. J Cosmet Laser Ther. 2006 Dec;8(4):197-202
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