Predisposing Conditions

Sun sensitivity of the skin is present in conditions such as:

Polymorphic Light Eruptions

This is a form of dermatosis of the skin that affects more women than men. Lesions of papules, plaques and vesicles are usually present on the sun exposed areas of the skin. These lesions appear to be more common in the spring and summer seasons and occurs approximately 24 hours after the skin has been exposed to the strong sunlight.

Actinis Reticuloid/Chronic Actinic Dermatitis

This is a rare condition affecting middle aged or elderly men. The area of the skin that is exposed to the sun becomes sensitive to light although the exact cause of this skin disease is not known. Thick plaques of dermatitis begin to develop when exposed to sunlight.

Solar Urticaria and Actinic Prurigo

Solar urticaria, similar to hives, is a rare condition that occurs on the sun exposed areas of the skin. The formation of wheals and skin itching occurs after the skin has been exposed to the sun. Actinic prurigo is a skin condition that begins in the early years of childhood with the development of papules and excoriations on sun exposed areas of the skin.

Treatment & Management

• The individual should wear protective clothing such as a sun hat or a long sleeve shirt on sunny days to protect the skin against sunlight, especially when outdoors.
• Avoid sunlight as far as possible to prevent any further development of lesions.
• Topical preparations of ointments or lotions containing local anaesthetics of benzocaine and other sensitizing preparations should be avoided.
• A course of systemic corticosteroids will decrease any discomfort although this offers only short term relief.
• An oral preparation of hydroxychloroquine reduces and suppresses the skins sensitivity to light.
• Sun block creams or sunscreens should be worn daily on sun exposed areas of the skin and applied many times in a day, especially after swimming.
• PUVA is effective in the treatment of polymorphous light eruptions and should be used on the sun exposed areas of the skin.

With regards to sunscreens, the main preventative agent in photodermatosis, it is important to monitor the sun protection factor (SPF) of your sunscreen. In most cases an application with SPF 15 to 30  may be suitable and higher SPF creams should be avoided as they may cause contact dermatitis. Rather combine your sunscreen with other sun protecting or reducing measures instead of choosing high SPF creams.

Following exposure to sun light, the epidermis increases its production of melanin to provide natural protection against sun exposure. This is seen as darkening of the skin or a tanning effect. Individual skin reacts differently when exposed to the sun making the comparison of light and sun sensitivity differ from person to person as the amount of melanin produced differs in each individual. While this hyperpigmentation may offer some natural protection against the skin, the cause of the light or sun sensitivity should nevertheless be treated.

Ultraviolet (UV) rays from sunlight can causes degeneration of the elastic fibres of the dermis (deeper layers of the skin) and thickening of the epidermis (outer layer of the skin. This thickening of the epidermis is usually caused by an increase rate of cell division due to heat and light.

While exposure to sunlight causes the condition, hot environments, certain skin diseases and drugs may make the skin more sensitive to sunlight.

Causes of Sun & Light Sensitivity of the Skin

Many factors may result in skin sensitivity to sunlight. These include :

Genetic Disorders

This genetic disorder has a family history of sensitivity of the skin to sun exposure. These disorders include genetic diseases such as Bloom’s syndrome which has instability in the chromosomal structure and a defect in the repair of the DNA molecules. This causes a reaction in the skin when it is exposed to the light.

Porphyrias

Porphyria is a rare metabolic disorder that due to an enzyme deficiency which leads to an accumulation of breakdown products of metabolism in the blood, urine and faeces. An accumulation of these metabolites can cause toxicity to the nervous system resulting in the skin’s sensitivity to the sun felt as burning and itching.

Pellagra

Pellagra is a condition due to a deficiency of nicotinic acid in the diet. This can cause light sensitivity of the areas of the skin exposed to the sun and diarrhoea may also be noticed after sun exposure.

Polymorphous Light Eruptions

This condition is caused by the skin’s reaction to sunlight and lesions such as papules, plaques and erythema multiforme appear on the affected area. It is sometimes referred to as a ‘heat rash’.

Drug Induced Sun Sensitivity

A condition that causes the skin to react when exposed to the sun due to the intake of certain drugs. Many drugs such as ACE inhibitors, tetracycline, thiazides and phenothiazines can cause eruptions of blisters, eczema, pigmentation and excessive sunburn on the light exposed areas of the skin. These reactions are caused either by the medication dosage or an allergic mechanism to the drug.

Topical Chemicals

Chemicals that have contact on the skin such as coal tar and plant derived psoralen can cause sun sensitivity of the skin. Coal tar which is used in the treatment of the skin condition called psoriasis vulgaris leaves the skin sensitive to sunlight. The plant derived psoralens found in carrots, fennel, and parsnips results in the light sensitivity of the sun exposed areas of the skin although the psoralen drug is used in the treatment of psoriasis. In both cases the skin appears with reactions of redness and eruptions of blisters.

Photodermatosis should not be confused with general skin irritation caused by the sun. Within 20  minutes of direct exposure to strong  sunlight, most skin types will show signs of inflammation, like reddening of the skin accompanied by a burning sensation. Treatment for photodermatosis should be undertaken by a dermatologist after the cause of the light and sun sensitivity is identified.