The benefits and the health risks of e-cigarettes are uncertain.[45][2][3] There is tentative evidence they may help people quit smoking,[83] although they have not been proven to be more effective than smoking cessation medicine.[5] There is concern with the possibility that non-smokers and children may start nicotine use with e-cigarettes at a rate higher than anticipated than if they were never created.[85] Following the possibility of nicotine addiction from e-cigarette use, there is concern children may start smoking cigarettes.[85] Youth who use e-cigarettes are more likely to go on to smoke cigarettes.[6][87] Their part in tobacco harm reduction is unclear,[7] while another review found they appear to have the potential to lower tobacco-related death and disease.[8] Regulated US Food and Drug Administration nicotine replacement products may be safer than e-cigarettes,[88] but e-cigarettes are generally seen as safer than tobacco products.[9][10] It is estimated their safety risk to users is similar to that of smokeless tobacco.[11] The long-term effects of e-cigarette use are unknown.[12][13][14] The risk from serious adverse events is low.[15] Less serious adverse effects include abdominal pain, headache, blurry vision,[16] throat and mouth irritation, vomiting, nausea, and coughing.[17] Nicotine itself is associated with some health concerns.[18]