Figure 31. Serum concentration of 25-hydroxyvitamin D in longterm sunscreen users and in age- and sex-matched controls from same geographical area. Blood samples were obtained simultaneously from patients and controls. Mean serum 25-hydroxyvitamin D level was significantly lower in long-term sunscreen users (p < 0.001). Two long-term sunscreen users had absolute vitamin D deficiency, 25-hydroxyvitamin D level below 20 nmol/L. PABA indicates p-aminobenzoic acid; open circles, subjects from Philadelphia; closed circles, subjects from Springfield, III. Reproduced with permission from.⁴⁸