Sand resistance of sunscreens.

Like water resistance in sunscreens, sand resistance in sunscreens is the ability of the sunscreen to retain its effectiveness while undergoing sand treatment. The influence of the type of sand on the sand resistance of sunscreens has not been described. The sand resistance of a control standard sunscreen, P2, and data on three grades of Quickrete commercial grade sand, #1961, #1962, and #1152, are described.

Water immersion does not alter the minimal erythema dose.

To determine the water resistance of a sunscreen, the COLIPA method requires the determination of two minimal erythema doses (MEDs): a static MED (MED(US)) and a wet MED (MED(UW)) (1). The MED(US) is used in calculating the static SPF; the MED(UW) is used in calculating the SPF after water immersion. Herein, we report that in the 107 subjects examined, the mean MED(US) (21.