Research has shown some scented candles produce smoke laced with almost as many toxins as those produced by cigarettes, according to Telegraph.

Since they are often lit in poorly ventilated rooms, such as bathrooms, or during the evening when windows are likely to be closed, the release of chemicals can cause indoor pollution that is potent enough to raise the risk of asthma, eczema and skin complaints.

More expensive varieties made from beeswax and soy rarely cause problems, but the majority of those sold are cheap imports made from paraffin wax, a by-product of the petroleum industry.