3. removal of the patches from the patient's back. 60 hours after the third visit, the participant will attend our department (forth visit). An ENT doctor will attach 3 patches to his back (the second type of patches: participant that had already in the previous visit lidoderm patches will now have the tegaderm patches and vice versa). 12 hours later the participant comes back for his fifth visit. The same 3 steps that were performed in the third visit will be performed again (4 questionnaires, patches removal, blood test for lidocain serum determination).