Bullous pemphigoid is an autoimmune disorder. If you have it, your immune system attacks healthy cells in your skin and mouth, causing blisters and sores. No one knows the cause. Bullous pemphigoid does not spread from person to person. It does not appear to be inherited. But some people’s genes put them more at risk for bullous pemphigoid. Bullous pemphigoid is most common in older adults and may be fatal for older, sick patients. Bullous pemphigoid usually occurs in elderly persons and is rare in young people.