Frequently and thoroughly applied sunscreen lotion is critical to protecting people spending time outdoors in the hot, dry, sun-drenched Southwest. Among experts advocating for sunscreen use is Paul Westerhoff, a Fulton Schools professor of environmental engineering. He says it’s especially important to keep lathering on the lotion that protects against the ultraviolet radiation in sunlight, especially if you’re in a pool, river, lake, ocean or other places where sunscreen can dissolve or be washed off. Westerhoff and a dermatologist  emphasize that some sunblock products don’t have a high percentage of actual sunblocking ingredients, like zinc oxide. So, it’s important to reapply heavily and often.