D o you sprinkle citrus zest on to your cooking or drink hot water with a slice of lemon? According to an Instagram post that went viral last week, you shouldn’t. “Select citrus fruits at Lidl now come with a ‘Peel unfit for consumption’ warning,” posts @wholefoodwarrior. She photographs some of the supermarket’s labels, which list the post-harvest chemicals used to conserve the fruit: azoxystrobin and fludioxonil (limes) and imazalil, 2-phenylphenol, thiabendazole, pyrimethanil and fludioxonil (easy peelers), plus E903 in the peel’s wax coating (both).

The 10,500 comments on the post are largely appalled. So what are these substances? And how worried should consumers be?

Sarah Compson, the head of policy and campaigns at the charity Pesticide Action Network UK (Pan UK), says that many of them are fungicides and known or suspected carcinogens and endocrine disruptors. For example, “Imazalil is a post-harvest fungicide used extensively on citrus fruit during storage and transportation,” she says.…