Photosensitivity is defined as an abnormal reaction of the skin to sunlight. Forty to 60 percent of Lupus Erythematosus (LE) patients are photosensitive. Excessive sun exposure may trigger the onset of disease, may cause flares in people who have systemic lupus and aggravate cutaneous (discoid) lupus.
Photosensitivity in lupus is usually caused by the sun's ultraviolet (UV) light: UVA, UVB, and UVC. The ozone in the stratosphere filters out UVC. Window glass filters out UVB and offers protection from the harm it can cause.
Almost all the effects of UVA and UVB are damaging. Exposure to UV causes aging wrinkling, pre-cancerous conditions and skin cancer and should be minimized by everyone on this on this basis alone. Cutaneous lesions of LE can be reproduced experimentally with both UVA and UVB light. While UVB is mainly responible for causing skin cancer and lupus, UVA also play a role. UVA can contribute to skin cancer, premature aging and is largely responibles for drug-induced photosensitivity. Both UVB and UVA can produce tanning.
Mechanism of UV Damage
Exactly how UV light aggravates lupus is unknown. Research suggests it alters DNA and protein in the skin. The altered DNA may act as an antigen that triggers the production of autoantibodies and provokes an autoimmune response in the skin. In photosensitive persons, UV exposure causes skin cells to release substances (cytokines, prostaglandins) that trigger inflammation. The skin reacts to these substances, becomes red, inflamed and develops a rash. Photosensitivity reactions can also affect the internal organs. In people with Systemic Lupus Erythematosus (SLE), the inflammatory substances released by skin cells can be absorbed into the blood stream and carried to other arts of the body. There, they may cause inflammation in organs and lead to systemic symptoms.
General Considerations
UV-induced lupus erythematosus is a medical and socioeconomic problem. Injury to people with LE in the work place can be a cause for Worker's Compensation and litigation. Each case must be individually studied and expert opinion obtained. There is no question that individuals who have lupus and are photosensitive should avoid excessive sun exposure. Delivering the amil, constrution work, and lifeguarding are examples of occupations that may receive excessive sun exposure. In addition, there are jobs where exposure to artificial sources of UV light can aggravate LE. Welders can be exposed to UVA, UVB and UVC in their work. Other sources of UV light in the workplace include photocopying machines, slide projector lights and TY studio lights provoking LE is not well documented but may occur in rare instances. A plastic shield over fluorescent lights blocks UV "leakage."
Sometimes trauma or injury to the skin may lead to the Koebner phenomenon where the skin reacts by producing LE lesions in the area of injury. Sunburn, thermal burn, lacerations and blunt mechanical trauma all can induce LE.
Photoprotection
Many factors contribute to photoprotection which is the ability of your skin to protect itself from damaging sun rays. Skin type is an important consideration. There are six classifications of sun-reactive skin types. Skin types 1 and 2 (burn easily tan minimally) need much more protection than types 3 and 4 (burn minimally tan readily). Skin types 5 and 6 (burn rarely tan profusely) do not need as much protection as other skin types. Types 5 and 6 contain larger quantities of melanin, a substance which darkens the pigment of the skin and has some sun protective properties. In Blacks, melanin has been said to have an SPF (sun protective factor) of 3 or 4. Blacks and Asians tolerate more sun, but can also experience photosensitivity. No matter what skin type an individual may have, precautions should always be taken.
Factors affecting the intensity of UV rays must also be considered. These include: time of day, altitude, proximity to the equator and reflective surfaces. During the mid-part of the day, the sun's rays strike the earth more directly and increase UV penetration. People should minimize outdoor activities between the peak hours of 10:00 AM and 4:00 PM. Ultraviolet radiation also increases nearer the equator, in the mountains or anywhere one is physically closer to the sun. There is less atmosphere to absorb the sun's rays and extra protection is needed. Reflective surfaces such as sand, snow and concrete increase exposure to UV light. Snow skiing or sitting on a sandy beach exposes one to a lot of reflected UV light. Snow or sand reflect about 50-75% of the UV rays. A person's UV exposure is significant even if they are sitting under an umbrella at the beach. An overcast sky does not reduce UV substantially and provides only minimal photoprotection from UV rays.
The simplest form of protection is clothing that can effectively block UV rays. Thin, loosely woven materials offer little protection because they allow UV to penetrate to penetrate to the skin. The tighter the weave, the better the protection. The thickness of the clothing is more important than color. When sun exposure is unavoidable, wear a hat, a long sleeve shirt and long pants. Umbrellas can also provide protection from harmful sun exposure.
Certain drugs can increase the body/skin's photosensitivity, causing undersirable skin reactions. Photosensitizing drugs include: acne medications such as tretinoin (Retin-A), diuretics such as chlorpromazine (Thorazine), oral antibiotics such as tetracyclines, sulfa drugs, hypoglycemics such as chlorpropamide (Diabinese) and non-steroidal anti-inflammatories such as Naproxen. The treatment for drug-induced photosensitivity reactions involves stopping the drug and/or using sunscreens and avoiding UV exposure. Whenever a new drug is prescribed ask your physician if it may cause photosensitivity.
UVA and UVB can both induce cutaneous (discoid) LE. Althought testing is rarely suggested, patients can be phototested to show how sensitive they may be to UVA and UVB light.
Sun-Protective Agents
Sun-protective agents can be sunblocks or sunscreens. Physical sunblocks are usually opaque formulas that protect by reflecting and scattering UV. They contain chemicals such as zinc oxide, titanium dioxide, and red veterinary petrolatum that block both UVA and UVB light. The most widely used UVA blocker is Oxybenzone. Sold as a white or a colored cream, sunblocks are particularly good for skiing and hiking at high altitudes. They are used very effectively on areas with extensive prior photodamage like the nose.
Sunscreens protect by absorbing UV light. They are available as creams. lotions or gels. The chemical content determines whether the sunscreen absorbs UVB, UVA or both. Chemicals that primarily absorb UVB include PABA (para-amino benzoic acid), and its esters, cinnamates and salicylates. Padimate-O, a PABA ester, is the most widely used UVB absorber. Benzophenones and anthranilates absorb both UVB and UVA. UVA protection is less well documented. Avobenzone (Parosol 1789), now available in the USA, is an excellent UVA absorber.
UVB sunscreens are rated according to their sun protective factor. An SPF of 15 protects the skin so it takes 15 times longer to produce erythema (redness) than it would without the sunscreen. SPF varies from 1-50; the most common strengths are 15, 30, 50. The price often increases with the SPF.
When purchasing a sunscreen consider the following: the SPF number, the type of UV absorbed and its ability to remain effective after application. While exercising, sweating, and swimming will decrease a sunscreen's effectiveness, there are "waterproof" or "water resistant" sunscreens. PABA and its esters are more waterproof than other sunscreens because they penetrate more deeply into the skin.
Sunscreens may produce side effects. Those which use alcohols or ethanol bases frequently are drying and may burn the eyes. The moisturizing lotions may appear greasy and aggravate acne. Other side effects include irritation and allergy. Irritation is common in products with an alcohol base. The most common allergen is PABA, although any sunscreen, by trial and error, which is acceptable. If the problem of allergy is difficult to solve, a dermatologist can help identify specific allergens by patch testing. PABA also tends to stain cotton, nylon, and polyester which may make it unacceptable. PABA does not absorb UVA and will allow tanning.
Before applying a sunscreen, first test the product on a small area of skin to rule out sensitivity or allergy. A sunscreen should be applied after shaving and applied and allowed to dry before puting on makeup. For the greatest protection apply it half an hour to an hour before going out in the sun. On average, a sunscreen will last about five hours, but should be reapplied if heavy sweating or exposure to water occurs. The lips should be proctected with either lipstick or a sunsceen with am ointment base. There are many bennefits of using sunscreen: sunscreens prevent skin aging, reduce the risk of skin cancer and protect against the photosensitivity reactions associated with lupus.
Summary
People with lupus should realize that a tan is not necessarily healthy. The sun "is their enemy." A sensible lifestyle includes minimizing excessive UV exposure and using photoprotection. Outside activities should be completed before 10:00 AM and after 4:00 PM when the UV rays are less intense. People with lupus should not sunbathe or use tanning booths. Those who work outdoors may need to change occupations.
Common sense should prevail. People lupus should be seither a "mole" nor a lifeguard. Through experience, each individual's skin type and degree of photosensitivity can be learned. Even if a person is not photosensitive, it is wise to be careful about sun exposure. By taking appropriate precautions and using common sense, individuals with lupus can achieve photoprotection.