The operating principle is the same for both radiation sources. The energy radiated into the skin is mainly absorbed by the pigment melanin. This pigment is contained in the hair but also in the skin. The energy of the radiation is converted into heat and transferred to the structures of the hair follicle responsible for hair growth. These are thereby destroyed, or their function (hair formation) is impaired.

In the ideal case, the damage is spatially limited to the hair follicle. It is thus selective. This process is therefore called “selective photothermolysis”.

It’s the colour that counts

The method works best when the hair contains a lot of melanin and the skin contains little melanin (i.e. dark hair and light to medium skin tones).

Red, light blonde, grey, or white hair contains little melanin. The desired permanent hair removal may not be achieved in these cases.

The darker the skin, the higher the risk of unwanted side effects or damage. This is because the device does not differentiate between the melanin in the hair and the melanin in the skin. In the worst case, it is not the hair but the skin that is destroyed.

Once is not enough

The treatment works successfully only on the hair follicles in which a hair is growing. Because this always only applies to a part of the follicles, the procedure must be repeated several times at intervals. The expectation of permanently preventing unwanted hair growth with a single treatment must therefore be disappointed.

This treatment uses optical radiation in irradiance levels or energy densities that pose risks to the eyes and skin. Visible radiation and infrared A penetrate the eye to the retina.

If the device settings are not adapted to the individual conditions such as skin type, degree of tanning, hair colour, and hair thickness, the following side effects may occur

• burns
• over- or under-pigmentation
• scarring.

This is often the case if the radiation intensity is too high and/or the treatment area is not sufficiently cooled.

Behaviour of customers or patients

The behaviour of customers/patients can also contribute to undesirable side effects. For example, if precautions or care instructions are not observed or if substances that increase sensitivity to light are taken or applied. The skin should therefore not be tanned before the treatment. Tea or medication with St John’s wort or similar substances that increase sensitivity to light should be avoided.

Caution with pigmented skin changes

Pigmented skin changes (e.g. birthmarks or liver spots) must not simply be superficially changed or removed with lasers or IPL devices. There is a risk that a diagnosis of skin cancer will be made more difficult or prevented. A prior diagnostic clarification by a dermatologist is recommended. Especially in the case of malignant melanoma, a diagnosis as early as possible is decisive for the success of the therapy.

Protection of the eyes is necessary

If the radiation hits the eye, damage is possible. The iris also contains colour molecules and can absorb the radiation. The wavelengths of visible light and infrared A used also reach the retina and can damage it. Eye protection must therefore be observed during the treatment.

Permanent hair removal with laser or IPL is offered by cosmetic studios as well as dermatologists or specialists for aesthetic–cosmetic medicine.

There are numerous devices on the market for home use. With these devices, the energy density to be achieved is usually lower than with professional devices.

Professional providers must be qualified

Anyone who uses lasers or strong optical radiation sources (e.g. IPL devices) on humans needs solid technical knowledge and expertise in order to avoid possible risks. The provider must be familiar with the equipment used and the effects of optical radiation and be able to adapt the treatment to the individual characteristics of the customer or patient. The provider must also be able to identify circumstances of the customers or patients that exclude the desired application or allow it only under strict risk-benefit considerations (contraindication). Examples of such contraindications are skin cancers or diseases that make the skin particularly sensitive to light.

With the Ordinance on Protection against the Harmful Effects of Non-ionising Radiation in Human Applications (NiSV) coming into force, only physicians are allowed to carry out some applications such as tattoo removal as of 31 December 2020. As of 31 December 2022 professional users must meet defined requirements in terms of technical knowledge.