Source: http://www.lupusil.org/lupus-keeping-you-indoors-this-summer.html

Lupus and the sun is viewed by many in the lupus community as compatible as oil and water.  It is well known that the sun can cause a lupus rash and a flare-up of systemic lupus with joint pain and internal manifestations. Studies have shown that about 40% of lupus patients are sun sensitive, but, of course, some are more sun sensitive than others.

Those with a history of rashes over sun-exposed areas such as the face need to be particularly careful about the sun and other sources of ultraviolet light.   Some lupus patients are may be too worried about sun exposure.

If sun exposure has not caused a flare-up in the past, people with lupus usually need not worry.  Some rheumatologists advise strict adherence to sun avoidance, whereas others are more lax, but most lupus flare-ups are not associated with sun exposure. Lupus patients shouldn’t become hermits, afraid to venture outside.

That said, sun protection is important for everyone.  Sunblock, including make-up with sun block, can be protective. But how much sun block is necessary?

The protective factor for sunblocks is decided by the company that makes the product rather than the FDA or another regulatory organization.  Companies are incentivized to beef up the protective factor score for sunblocks, and so, in testing situations, they tend to glob on huge amounts of sunblock that form a very thick layer and then do the test for the sun protective factor – providing an inaccurate score.

The FDA has new rules governing sun block, which go into effect in about one year, that will ban certain labels such as “sunblock”, “waterproof”, and “sweatproof” because these words apply a false level of protection.  One of the FDA rules is that to use the term “broad spectrum” the sunblock must cover UVA and UVB radiation adequately. (There are two kinds of solar radiation: UVB rays cause burning while UVA rays cause wrinkling.  Both types can cause cancer.)

For now, in general look for products with a sun protective factor between 30 and 50 and with the words “broad spectrum.”  Sunblocks should be water resistant, and reapplied after about one hour, depending on the product.  Wearing hats and staying out of the sun especially the mid-day sun, are advisable.  Currently, sunblock products with SPFs over 50 can expose people to additional irritating sunscreen ingredients, but do not necessarily provide meaningful added protection.

When the new FDA rules go into effect, a sun block with a sun protection factor of 15 or higher will be able to claim a reduction in risk for skin cancer and early skin aging.  Consumers will be better able to choose a sunscreen based on the SPF number and make sure that it is broad spectrum.

Sunscreens do prevent squamous cell skin cancer and melanoma.  Melanoma is the most serious type of skin cancer.  Sunscreens may not protect against the first case of basal cell carcinoma, but appear to delay recurrences of basal cell cancer.

Because humans often sweat off part of the sunscreen and also do not use the same quantities as in testing situations, the sun protective factor is only a guide to the strength of the sunblock lotion or cream.  Nonetheless, sunblock is very helpful, but should be reapplied on hot days when people perspire a lot.  Protective clothing including hats, longer sleeves, long sleeves, and long pants are also advisable for some certain patients.

If a lupus patient does get a rash provoked by the sun, usually steroid creams and, occasionally, oral prednisone are used for treatment.  Stronger skin steroid creams can cause mild skin atrophy with prolonged use.  For longer use on the face, hydrocortisone 1% cream is recommended.  For short-term use, stronger steroid preparations can be used.

There are other forms of skin lupus aside from the systemic lupus rash, which often involves the face and frequently the hands and other sun exposed areas.  These include discoid lupus, in which there are disc or plate-shaped scaly lesions on the skin, and a form of skin lupus called subacute cutaneous lupus with extensive skin lesions.  It is less clear that these other forms of skin lupus are directly related to sun exposure, though it seems wise to avoid prolonged sun contact in patients with these conditions.