I was hoping to get a response back from you about your dog, but I don't want you to have to wait for an answer either. Usually sent a dog acts like this, they are a dominant dog . He probably feels like Your bedroom is his territory and he doesn't want your son in his area. It is likely he would also bite your son at other times as well if he felt your son needed a reprimand.
You can correct this with training. First he needs to be obedience trained. The following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
You should train him and then have your son also help with training once your dog knows some commands. Even if your son is young, if he can say sit and throw a piece of hot dog, he can help. That will get the dog seeing your son as the boss as well as you being the boss. Dogs do not reprimand (bite) the boss. It will take some time for the training to work, but the dog will respect your son then.
In addition, leash your dog and do some special training. Each time your dog barks, growls or is aggressive toward your son, give him a short tug for a correction and tell him “NO” in a low firm tone. Dog’s growl when they are commanding other dogs which is why you used a low firm tone. Do this each time. I realize it may be an ongoing battle. You may do training where your son comes in the room, you make the correction and your son leaves immediately. Make the correction as soon as he starts to show aggression. Have small tasty treats like hotdog slices ready. If your dog does not bark at your son, praise him and give him a small treat. Practice this often. Each time he doesn’t bark, give him a treat. Before you know it, he’ll be associating your son and not barking with getting treats and praise. At this point you will want to cut back on the treats and make them a sometime reward with the praise being the reward. Remember, the correction should not be hard, or choking, just a quick short tug, to break his concentration while you tell him “NO”.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer so I am compensated for my time.
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Since there have been recalls on certain foods, please check the following site to be sure the food your animals eat is not affected. If it is affected, contact your vet as soon as possible. Have your dog seen if they have any symptoms.