My friend has chronic halitosis and a white tongue. is it contagious?

Halitosis: The most common cause of halitosis is poor oral hygiene and lack of dental care. The white patches may be food debris on the tongue or possible a thrush infection. If your friend has not seen a dentist have them start with a dental exam. If this is the case then it isn't contagious and you should not worry. Just keep on brushing and flossing your teeth.

Simple solution: In the majority of cases, the cause of bad breath, or halitosis, is the product of bacteria in the mouth. The proper diagnosis is the key to a successful treatment. See your dentist for Halimeter test, diagnosis and bad breath treatment that depends on its cause. Good luck.