Sun exposure is probably the biggest thing to watch out for with laser treatments. You need to avoid direct sun for at least 2 weeks before and after each session. Tanned or sunburned skin increases the risk of burns, discoloration, and other complications because the laser can't distinguish between the melanin in your hair and the melanin in tanned skin. If you're planning a beach trip, you'd want to either complete your treatment series well before or wait until after. Most clinics won't treat tanned skin for safety reasons.