Heliotherapy

What is heliotherapy?

Heliotherapy is the use of natural sunlight for the treatment of certain skin conditions. It is a form of phototherapy. It is also called climate therapy.

How does heliotherapy work?

The ultraviolet (UV) part of the sunlight spectrum has beneficial effects in small doses.

• Short wavelength UVB and longer wavelength UVA induce vitamin D production and other chemicals that protect skin cells.
• The UV radiation is anti-inflammatory, immune suppressing, and antiproliferative.

The daylight part of the sunlight spectrum can also be useful in the treatment of skin conditions, for example in combination with the photosensitising agent, methyl aminolevulinic acid, for "daylight" photodynamic therapy (PDT) to treat actinic keratoses.

What skin conditions respond to heliotherapy?

Inflammatory skin conditions treated with heliotherapy are similar to those treated with other forms of phototherapy.

Psoriasis

Heliotherapy has been found to reduce the extent and severity of psoriasis and to improve the quality of life for patients. It rarely completely clears psoriasis, and in 10%, sun exposure aggravates psoriasis.

Atopic dermatitis/eczema

After 2–4 weeks of heliotherapy, there may be an improvement in atopic dermatitis/eczema immediately after treatment and several months afterwards. Note that sunlight can also result in photoaggravated eczema.

Other skin conditions

Other skin conditions such as vitiligo have also traditionally been treated with sunlight. Heliotherapy may be combined with topical or oral trisoralen (see PUVA), which enhances the effect of sunlight alone, but also increases the risk of sunburn and may cause side effects such as pigmentation.

Benefits of heliotherapy

Benefits include:

• Heliotherapy is available everywhere, although it is weather and climate-dependent.
• Heliotherapy is affordable, especially in countries where phototherapy is inaccessible

Disadvantages of heliotherapy

Disadvantages of heliotherapy include:

• Side effects: sunburn, the risk of photosensitivity reaction, long-term skin ageing and skin cancer
• Variable dose: the amount of UV in sunlight is dependent on latitude, ozone amounts, seasonal variation, time of day, cloud cover, rain, and the aerosol content of the air.
• Variable exposure time for an individual: this is dependent on their Fitzpatrick skin phototype, prior exposure to UV radiation, the presence or absence of photosensitivity, and the condition being treated.

How to use heliotherapy

General points:

• Avoid excessive sun exposure. Heliotherapy is not suitable for very fair skinned or photosensitive individuals. Note that the sun is a class 1 carcinogen.
• Undertake exposures at the same time/s of day, each day.
• Continue prescribed treatment (check with your dermatologist).
• Continue regular emollient use.

Regimens include:

• Dead Sea Basin method: 10–20 minutes exposure twice daily, with daily increments of 10 minutes to reach a maximum of 3–6 hours per day (depending on geographic location and other factors). Recommended for a total of 3–4 weeks.
• Minimal erythema dose (MED) method: the MED can be determined for the patient. This is the dose or time exposed to the sun that is required for the skin to be just discernably pink 24 hours after exposure. The subsequent increase in dose/time depends on the Fitzpatrick skin phototype of the patient. Note: MED will be accurate only for the time and day on which it was measured.

Refer to your local reports of ultraviolet radiation levels. In New Zealand, the sun protection alert warns people to protect themselves during certain times of day during the summer months. Global Solar Ultraviolet Index (UVI) describes the level of solar UVR at the Earth's surface in different locations. Safe exposure can be calculated using a smartphone app that displays geographically and Fitzpatrick skin-type specific real-time UV levels.

The Dead Sea Basin

Traditionally, the Dead Sea has been used as a location for heliotherapy, particularly for psoriasis patients. The sea is approximately 400 m below sea level therefore selectively filters UV radiation, leaving a higher concentration of UVA to UVB than found at sea level. Furthermore, the Dead Sea has an ideal climate to be outdoors, with moderate to high temperatures, low humidity, a large number of sunny/cloudless days and low rainfall per year. This allows the use of the sea for treatment at least 8 months of the year.