Hi There, I was wondering if i could get some advice. Currently my 2 year old St Bernard is getting increasingly more aggressive and i have no idea why. He has a real issue with people he doesn’t know. He is so lovely and affectionate once he recognise you but before he reaches that point he is so angry. It is starting to become a real problem because now no one new can now enter the house. Before he would just bark at people. But over the last few months he has started to lunge and is attempting to bite. This is strictly with Males, Females he has no issue with. He is at his worst when someone enters the house he does not know. He will hear the doorbell ring sit at the top of the stairs and await for them to come in. He then proceeds to come down the stairs to sniff, if he does not like what he smells/sees he will start to bark very angrily. This will then move on to trying to lunge and bite. I then have to put him on the lead and introduce them very slowly till he stops growling as people in the house approach. But today i tried this with my dad (who he has met before) and it did not work. He lunged at him and bit him ripping his shirt but luckily no damage was done. What do i do? He was never like this growing up but now it is really starting to have a negative affect on my life. I am always on edge around new people and whenever guests are coming round i usually send him away or put him in another room.