Rabbit Anti-German cockroach Bla g 1 antibody for ELISA, Crystallography. Bla g 1 is an allergen associated with the cockroach B. germancia. Its allergenic nature may trigger allergic reactions in susceptible individuals. Allergen levels may be quantified by ELISA. Sensitive individuals have allergic responses to this protein which is thought to play a role in the digestive system of the insect. The cockroach allergen (Bla g1) has been shown that it can cause sensitization at approximately 1 U/g house dust and can cause asthma symptoms in sensitive individuals at concentrations as low as 8 U/g.