Thiomersal belongs to the class of medications called as preservatives. It is used in minuscule quantity in some vaccines (e.g. tetanus and pertussis (DTP), diphtheria and tetanus toxoids (DT)) and works by preventing bacterial and fungal growth.
Irritation of ear, Allergic skin rash
Thiomersal is used in preservation of the medicinal products.
Yes, thiomersal contains ethyl mercury and is considered safe with no studies indicating it as harmful. It is used in few multi-dose vaccines.