The Tanning Question

As those of you in the UK are aware, we've just had the hottest weekend of the year so far. Upon seeing Nick (IT guy) sporting the tan that he'd gained, Susan asked..

"Have you been using that self-tanning cream?"

How do you answer that without patronising the questioner? Evidently Nick wasn't concerned with tact and gave an response that included the phrase "big fuck-off fiery ball".