Although side effects of vitamin B1 are rare,some people may experience anallergic reaction. Ifthe side effects include a rash, inflammation of the face, swelling ofthe tongue, feeling faint or breathing problems,the best solution is to seek immediate medical attention for treatment, reports MedicineNet.
Other possible side effects like chest pain and bloody stoolrequire a doctor visit, relates eMedicineHealth. In cases where thiamine is injected, a possible side effect is the formation of a lump at the injection site. This is a less serious side effect,for which a person may call his or herdoctor.
Vitamin B1 is called thiamine. Although this vitamin is found in many foods, there can be deficiencies of thiamine in certain people, states WebMD. Certainconditions like beriberi, alcohol withdrawal,neuritis and some digestive problems benefit from thiamine treatment.