Background Thirdhand smoke (THS) represents the accumulation of secondhand smoke on
indoor surfaces and in dust, which, over time, can become more toxic than secondhand
smoke. Although it is well known that children of smokers are at increased risk for asthma or
asthma exacerbation if the disease is already present, how exposure to THS can influence
the development or exacerbation of asthma remains unknown. Objective We investigated
whether epicutaneous exposure to an important component of THS, 4-(methylnitrosamino)-1 …