Third hand smoke is the smoke residue left in the environment after a cigarette has been extinguished. This residue can have serious implications for people with asthma, triggering attacks and aggravating symptoms. A new study has found a link between third hand smoke and asthma in children, with those exposed to the smoke being more likely to be diagnosed with the condition compared to those who had no exposure. The study also found that exposure to third hand smoke could lead to an increase in the severity of asthma symptoms. The findings are important for parents, as it highlights the need to keep all smoking away from children, even after the smoke has gone.