There is no definitive answer to this question, as everyone’s skin is different. However, it’s generally recommended that you don’t spend more than 15 minutes in the sun or on a sunbed at a time, at most once per day. That’s because overexposure to UV rays can damage your skin and lead to health problems like skin cancer. If you do want to tan for longer periods of time, make sure to use sunscreen and take breaks so that your skin doesn’t get too much sun exposure. In the U.K. tanning salons tend to use bulbs that do not emit UVB radiation which is commonly associated to the risk of skin cancer. It’s recommended that you don’t use a sunbed more than 2 or 3 times per week and no more than once in a 24 hour period.