KARWAR: A father-son duo from Sirsi consumed an immunity boosting concoction, which resulted in the death of 42-year-old son. The 70-year-old father is battling for life in a hospital. The herbal concoction is known to build immunity, if the right herbs are consumed in the right proportion. It’s a case of probable mistaken identity of a herb which has led to the death of a person, sources said. Francis Rego from Ramanabailu consumed the mixture along with his father Necklam Anthony fearing coronavirus infection. According to the police, the son died within a few minutes and the father was rushed to a hospital.