Bath bombs will get less effective as time goes on. The fresher they are, the faster they'll fizz, says Jack Constantine, head of product development at Lush.
"We have fanatics who'll keep theirs wrapped and in tupperware boxes underneath their bed, for years – which is extreme," he says. "But you can do it, as it's about the freshness. If the bath bombs are out on display, they're oxidising and they're losing the ability to react so well. So the citric and the bicarb start to bind. The fresher they are, the faster they fizz.
"Our freshness policy in the factory is 21 days. So if you buy off the website, it's normally seven days at a push [i.e., your product has been made within seven days]. We will get complaints from people who say, 'I bought this a year ago, I chucked it in and it did nothing!' You need to use it. The same with the smell – the smell will wear off as all the essential oils start to evaporate."