Eating Jalapenos in moderation is very healthy for you and can prevent diseases such as cancer and can even boost your immune system.
But when you do consume too many Jalapeno pepper it can lead to stomach problems and eventually yes ulcers as the Jalapeno peppers when consumed too much or too often can eat at your stomachs lining and cause other stomach problems.
However I've heard that if you do just eat the Jalapeno peppers in moderation they can help prevent stomach ulcers from occurring but when eating too many of the Jalapeno peppers it can lead to stomach ulcers.
So just eat the Jalapeno Peppers in moderation and you'll be okay.
But if you already have stomach ulcers it's best to avoid eating Jalapeno Peppers because it can aggravate the stomach ulcers.