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Friday, March 6, 2015
Skin Care and Diseases
Shelf life of suntan lotion
Is there an actual life of tanning/sunblock after opening the bottle? My girlfriend insists upon replacing it year to year saying that after a year,it turns into a moisturizer rather than a protectant.
If you look on the label and/or the bottom of the container you will see an expiration date for the preparations that you have purchased. These are dates that suggest optimum activity, and potency can be guaranteed until that date if the bottle or container is not opened. Once it is opened, deterioration is accelerated, and even though there are antibacterial agents / stabilizing agents in the preparation, they do tend to deteriorate. I think your girlfriend is probably correct in replacing suntan preparations on an annual basis so as to guarantee potency and expected results. As to what happens with the break-down products I think you would have to contact the manufacturer; but I would agree with her that maintaining fresh material is the best policy.
Charles L Heaton, MD
College of Medicine
University of Cincinnati