evidence: You may very well be sensitive to one of more of the ingredients in the flu shot.. Sime multidose vials contain thimerosal which is 50 % mercury and a potent neurotoxin. You could be sensitive. [...] Influenza (Flulaval) Trivalent & Quadrivalent ovalbumin, formaldehyde, sodium deoxycholate, α-tocopheryl hydrogen succinate, polysorbate 80, thimerosal (Mercury)(multi-dose vials) [...] Not trying to be alarmist - but for those who live in the USA it would be good if they have the single dose flu vaccine as the multidose vial can contain the Mercury containing thimerosal. Always good to check the full ingredient list in vaccines.