Q Laser and ultrasound seem to be two techniques for permanently removing unwanted hair, but are these techniques safe and effective? Is one safer than the other, and what are their potential side-effects (other than a hole in your wallet)? - LH, Hong Kong
A There are three hair-removal techniques that claim to be permanent - laser, electrolysis and thermolysis - and each comes with its own problems and side-effects.
The laser technique involves passing a beam of light through the skin and heating the hair follicle, thereby damaging it. But around six treatments are needed to cause permanent damage to the follicles.
With electrolysis, a tiny needle is inserted into each individual hair follicle and an electric current is passed through it, so damaging the follicle.
The third method, thermolysis, is similar to electrolysis, but uses heat passing through a needle to destroy the follicle.
Laser treatment is ideal for larger areas of the body, such as the legs or back, and if the hair is dark. But you need to know about skin type and lasers before you start.
All lasers work on the principle of photothermolysis, in which laser energy destroys a follicle's ability to grow new hair. The energy is absorbed by the pigment that gives hair its colour - eumelanin in the case of brown and black hair, and pheomelanin if your hair is red. Your skin colour also determines how much infrared light is absorbed (Semin Cutan Med Surg, 2000; 19: 267-75).
If you know you are sensitive to light (photosensitive), or have had keloidal scarring (where a thick, puckered, itchy cluster of scar tissue develops, extending beyond the edges of a wound or incision), endocrine disorders, allergies, infections or herpes simplex, then you are more likely to develop scarring after treatment.
Your skin type is usually determined according to the Fitzpatrick Classification System, which gives you a rating score according to the amount of pigmentation and tanning. The lower the rating score of your skin type, the less melanin you have in your skin and the lower your risk of skin damage as a result of laser therapy.
Next, you need to investigate the type of laser that will be used. The normal-mode ruby laser (wavelength 694 nm) is not found in many salons because of its size and cost. It also generates an enormous amount of heat, which can result in a rather unpleasant experience. This laser can also cause skin irritations such as redness (erythema) and swelling (oedema) in virtually every case, although these usually disappear within 48 hours. Blistering and hyper- or hypopigmentation is seen in around 5 per cent of cases, especially if you are dark-skinned.
A more popular laser is the long-pulsed alexandrite laser (wavelength 755 nm), which can remove about 75 per cent of hair after five treatments or so. It is a safer laser for fair-skinned people.
A device known as the 'non-laser light source' (wavelength 550-1100 nm) is not commonly used because it is difficult to operate. If such a device is to be used on you, make sure the technician has been properly trained. The non-laser light source can remove up to 63 per cent of the hair after four treatments.
The Nd:YAG (neodymium:yttrium- aluminium-garnet) laser (wavelength 1064 nm) produces quick, and impressive, results. However, it isn't always permanent, with some patients reporting hair growth some three months after the procedure.
The Nd:YAG is ideal for dark-skinned people. When it was tested on 17 women, it was found to be effective, achieving an 84-per-cent hair loss after three months. Researchers also claimed the laser was safe, although no explanation was given as to why, in this particular study, three women were not available for the follow-up visit. Also, as there was no longer-term monitoring of these women, it is not known whether the hair loss was permanent (Arch Dermatol, 1999; 135: 668-76).
Finally, the diode laser (wavelength 810 nm) is also ideal for darker-skinned individuals, and claims to produce significant hair loss after several treatments.
The US Food and Drug Administration (FDA) has recently approved for use a number of different lasers, but has described them as 'permanent hair reduction' devices. The FDA does not support the claims of practitioners that these lasers can achieve permanent hair loss. American practitioners are also forbidden to state in their marketing material that the procedure is painless.
One major concern, in the US and elsewhere, is that this is an unregulated market, and practitioners with no experience can open a salon and begin treating people.
While lasers have been used for hair removal for only a decade - they were first approved by the FDA in 1995 - electrolysis is a treatment that has been around for well over a century. The first reports of its use go back as far as just after the American Civil War. Some practitioners believe it to be safer and more effective than laser treatment (BMJ, 1972; 813: 591-2), but some of its claims are exaggerated - and unsubstantiated.
Electrolysis uses three types of energy. Galvanic electrolysis works by causing salt and water in the skin around the probe to be chemically altered to produce a small amount of sodium hydroxide, or lye. Lye is the active ingredient in some household drain cleaners (www.hairfacts.com). If enough lye is produced, it can damage the cells responsible for hair growth.
Another variation of the technique is thermolysis, which causes the water molecules around the probe to vibrate at high speed, thus creating heat. If sufficient heat is produced, the follicle will be damaged.
Finally, an approach known as 'blend' is based on the fact that lye becomes more caustic when heated. This method is recommended by some experts (Richards RN, Meharg GE, Cosmetic and Medical Electrolysis and Temporary Hair Removal, Toronto: Medric, 1991), but it takes a very skilled practitioner to perform the treatment safely.
Because it treats every single hair follicle individually, electrolysis is better suited for smaller patches of skin, such as the bikini area or the eyebrows. But, as a result, it is also slow, tedious and very expensive.
It is also important to check the credentials of the practitioner because, if it's not performed correctly, hair can grow back, the surrounding skin can be permanently damaged (Hautarzt, 1973; 24: 203-4), and it can cause the spread of skin infections (Plast Reconstr Surg, 1998; 101: 504-6) and skin lesions (Cutis, 1980; 26: 85).
Although most people do enjoy permanent hair loss with electrolysis, up to 10 per cent of patients have complained of hair regrowth (J Am Acad Dermatol, 1995; 33: 662-6). Salon claims of a guaranteed zero-per-cent regrowth have never been proven in any proper scientific trial.
Electrolysis seems particularly successful at removing underarm hair. One study from Japan reported 'little to no regrowth' at six to 36 months after three to eight electrolysis treatments (Aesth Plast Surg, 1987; 11: 223-7). Another Japanese study, using the blend technique, reported no regrowth at six months after seven to 14 treatments, while comparative plucking resulted in no significant hair removal after six months (J Dermatol, 1995; 22: 738-42).