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how the seasons affect psoriasis

As many as 70 percent of psoriasis patients experience a worsening of symptoms from late fall into the winter, according to Susan Katz, MD, clinical assistant professor in the Ronald O. Perelman Department of Dermatology at NYU Langone Medical Center in New York City. “There is a decrease in humidity and dropping temperatures, which dries the skin. There is also less UV light available.”

“Winter is worse because there is not as much sun,” agrees Jessica Kaffenberger, MD, a dermatologist and director of medical student education at The Ohio State University Wexner Medical Center in Columbus. “Sunlight dramatically improves psoriasis.”

There is a scientific explanation for the connection between the weather and psoriasis symptoms. According to the National Psoriasis Foundation, certain genes are turned on at different times of the year, depending on where you live. In other words, your immune system produces proteins that can launch an inflammatory attack against something that may be harmful.

People who live in Northern Europe, for example, have an active immune system in the winter. In contrast, if you live in West Africa, your immune system kicks in during the rainy season (the summer months), when infectious diseases such as malaria are the highest. It appears your immune system knows where you live and when your seasons occur. Of course, you want your immune system to help keep you healthy in the face of flu or malaria. But if you have an inflammatory disease such as psoriasis, an active immune system can also trigger symptoms.

Exposure to ultraviolet light B (UVB), found in natural sunlight, is so important in easing psoriasis symptoms that many patients undergo prescription light therapy during the winter months. Dr. Kaffenberger says about three days of medically supervised light therapy each week at a doctor’s office or psoriasis clinic can dramatically improve symptoms.

That said, there is a small portion of patients for whom psoriasis does not improve with UV exposure. Kaffenberger says doctors are not yet sure why this is.

It’s important to point out that the light boxes used to treat psoriasis are different from tanning beds. Dermatologists do not advocate tanning beds (which significantly raise your risk for skin cancer) for psoriasis patients — or anyone else for that matter.

Dr. Katz recommends liberally moisturizing your skin in the winter with an unscented moisturizer, preferably one that does not have many preservatives. A home humidifier can also help prevent dry winter skin.

You’ll also want to take steps to keep yourself healthy and avoid infections, the flu, or anything that might trigger your immune system. Wash your hands frequently, eat a healthy diet, and get plenty of sleep. Ask your doctor whether a flu shot is right for you, and find effective ways to manage your stress, as it is also a significant trigger of psoriasis symptoms.

Staying healthy is especially important for children with psoriasis. Katz says there is a strong correlation between strep infections and a type of psoriasis called guttate psoriasis. If your child has psoriasis, seek prompt medical attention if they develop strep throat.