Nature Made Vitamin B12

This is the vitamin B12 that I make sure to take every day. It is a product from Nature Made, a well-known brand for supplements. I order it directly from the US and take it. When I feel tired or my immune system weakens, blisters appear around my mouth and inside my mouth, but I heard that B vitamins are effective in prevention. I have actually been taking it for over a year, and I think I get fewer mouth ulcers haha.