Treatment for PMLE depends on its severity. Other than staying out of the sun and protecting yourself when you are in the sun, you may not need treatment. The rash can clear by itself within 7-10 days.
To treat or prevent PMLE, you may also need:
Steroids that go on your skin
Sunscreen that says "broad-spectrum" on the label
Phototherapy with psoralen UV light (PUVA) to desensitize skin to UV light