Sometimes these things are subconscious and can't be helped, except by professionals. I had a friend that couldn't eat chicken or in fact any fowl. He called around one day as we were getting some tea on and he stayed to eat. We were having turkey sausages. I could either have told him and he wouldn't have eaten, or not and he would eat them. I chose the second option. Two days later, when the sausages had well and truly been and gone through him, I thought I'd tell him and he would realise that it was all in his mind and he'd be cured. I did tell him and he was then promptly violently sick! Oh well.