Hi doctor, My father is suffering from a sudden attack that happened to him recently . He is allergic to histamine and what ever contains histamine will make his body swollen (e.g. His tongue,his face).What would you recommend for him to take as anti-histamine? For example he tried Xyzal, but still parts of his body become swollen. I am really worried that even if he is under medication and he is following a certain diet ( he tries to avoid the food that contains a high level of histamine) , he is still swolling. Please mind that he has asthma also.