By Aries Poon

When a baby is born, its mother may find a part of its skin carries an abnormal colour, a birthmark. Many years ago, some people believed that the baby was struck by evil spirits. Even now some mothers may blame themselves for being careless during pregnancy, thinking maybe a birthmark is due to jarring the baby in the womb.

Especially when it comes to birthmarks that are exposed to public view, some mothers feel a strong need to have them removed.

The Prince of Wales Hospital has brought a new laser system for providing economical birthmark removal for the public. Some other public hospitals and private clinics already have similar technology.

Dr. Lam Lai Kun, consultant of the Department of Surgery at the University of Hong Kong, explained how laser does its job.

The word laser is the abbreviation of Light Amplification by the Stimulated Emission of Radiation. When light is stimulated into an excited state and then back to the normal state, energy, which is commonly known as radiation, is given off. The laser emitter is used to control and arrange the light beams into a parallel pattern.

When laser light is absorbed by the birthmark, light energy is changed into heat energy. The heat then vaporizes the lesion skin tissue.

“Actually, this is no different from burning away birthmarks,” said Dr. Lam.

Only abnormal tissue is burnt because different substances absorb radiation at different wavelengths.

Such a surgery is not completely successful. “The process is not free from problems,” said Dr. Lam. “Laser is an abrasive agent. If you want to totally erase a lesion which is extensive and deep in the skin, the price to pay is a big scar.”

The laser actually leaves a burn. Patients may be subjected to infections. Once healed, a scar may exist when the skin lesion is originally deep and diffused. Also, the pigmentation of cells may change. They may turn even darker after the surgery.

A birthmark is formed when there are problems of cellular differentiation in blood vessels or skin pigment cells during the development of embryo. If the process of blood vessel differentiation is disturbed, some fine blood capillaries are deformed. The resulting vascular birthmark usually appears to be deep purple and apparent. Some may even rise up and spread onto the skin surface.

Another kind of birthmark is formed when the skin’s pigmented cells abnormally increase in number or contain extra amount of pigment. They are usually in a dark colour. Such a birthmark is called nevus in medicine, which is also commonly known as mole.

The reasons why the cells do not differentiate orderly have not yet been found out, at least with the present level of knowledge and resources. The factors may be genetic, environmental, or prenatal.

“Birthmarks do not affect one’s health,” said Dr. Lam. “This surgery is usually for cosmetic significance. People ask for this surgery usually because they are suffering from exposed birthmark on their faces, necks or hands. I think if it is not an exposed one, people tend not to come to us.”

An exposed birthmark might impose detrimental effect on one’s psychological state. Some the social psychologists concluded that physical attractiveness plays an important role in how much each person is liked by his or her partner. Relieving a birthmark probably improves one’s psychological state.

“The demand for erasing birthmarks is probably low,” said Dr. Lam. “If birthmarks occur randomly, the probability of having exposed birthmark is quite small. But I cannot provide scientific conclusion to the public demand for this surgery. It is only my personal observation.”

November 1996

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