Unpredictable and irritating, psoriasis is one of the most baffling and persistent of skin disorders. It's characterized by skin cells that multiply up to 10 times faster than normal. As underlying cells reach the skin's surface and die, their sheer volume causes raised, red plaques covered with white scales. Psoriasis typically occurs on the knees, elbows, and scalp, and it can also affect the torso, palms, and soles of the feet.
The symptoms of psoriasis vary depending on the type...
"In general, people with psoriasis do better in summer for two main
reasons -- No. 1, there's greater humidity, which helps keep the skin moist,
and No. 2, there's more sunlight exposure," says Bruce Strober, MD,
director of the Psoriasis and Psoriatic Arthritis Center at NYU Medical
According to the National Psoriasis Foundation, psoriasis develops when the
regular system of cell turnover goes awry.
Normally, skin cells are shed every 28 to 30 days and immediately replaced
by new ones. In psoriasis patients, however, this process is speeded up
dramatically, with cell turnover occurring as quickly as every two to three
This, say experts, causes a kind of biological "traffic jam,"
causing old, dry skin cells to literally pile up on one another, forming the
When the air is humid, Strober tells WebMD, the skin is better able to
retain moisture, which is key to easing those dry plaques. Moreover, he says,
since UVA is a recommended treatment for psoriasis, the natural UVA rays of
summer sun can be therapeutic.
That said, experts also tell us there are some summer precautions psoriasis
patients need to heed. Among them, a reminder not to overdo time in the sun no
matter how much you think it can help.
"You do not need excessive sun exposure to effectively treat psoriasis
-- 30 minutes per day of natural sunlight is more than adequate -- and
overdoing it could cause significant problems, not only increasing your risk of
skin cancer, but sometimes making your psoriasis worse," says Strober.
That's because even a slight sun burn, says Strober, can damage the skin.
And that not only worsens psoriasis plaques but can also cause new ones to
"Essentially, sunburn can cause normal skin to turn into psoriasis skin
because of the direct damage to skin cells," says Ellen Marmur, MD, chief
of dermatologic and cosmetic surgery at Mount Sinai Medical Center in New York
Experts say a unique aspect of psoriasis known as the Koebner phenomenon
also plays a role. In this instance, any break in the skin or damage to skin
cells can exacerbate that rapid cell turnover, causing new plaques to develop
at the site of the damage. Experts say excessive sun exposure, which can cause
sunburn, can do that kind of damage.
Psoriasis Sun Protection Advice: What to Use
To maintain the benefits of sun exposure while preventing problems, Marmur
recommends liberal use of sunscreen, or, if possible, a sunblock, for complete
"A lot of people don't realize that sunscreen only offers protection
from UVA rays -- to get protection from both UVA and UVB rays you need to use a
sunblock, which not only reduces your risk of skin cancer, but also prevents
the kind of cell damage that causes psoriasis to flare," says Marmur.