How Is Acne Affected by the Weather?

For people with light skin, a good tan can cover up many skin imperfections, whether they are pimples or cellulite. And the rays of the sun pack a 1-2 punch against acne. Light in the blue-violet spectrum (410 to 420 nanometers wavelength) kills Propionibacterium acnes bacteria, and ultraviolet light slows down the action of the immune system, reducing inflammation.

But getting so much sun that you “dry out” the skin actually makes acne worse. Overall, there are more negatives than positives with sun exposure.

Ultraviolet not only damages DNA in acne bacteria so that they cannot multiply, it also damages DNA in your skin. This sets the stage for sun spots and skin cancer. Tanning thickens the layer of skin known as the stratum corneum. This is the layer of skin that lines hair follicles. Thickening this layer of skin tightens pores and forms comedones. That is why so many people have the worst acne of the year in October in the northern hemisphere, and in May in the southern hemisphere.

The combination of moist, tropical air and strong sunlight can cause “tropical acne,” a condition that was so bad for some soldiers in the Vietnam War that they were mustered out of the service and sent home. Dry, cold winter wind can also constrict pores and create comedones that turn into whiteheads and blackheads.

A little sunlight nearly every day is essential for getting your vitamin D, and skin that is covered with sunblock doesn’t make the vitamin. More than 20 minutes of sun exposure a day, however, requires sun protection.