If i drink cold water or in cold weather it causes pharyngitis how to improve my immunity?

Never heard of it.: Never heard of cold water causing pharyngitis. However you may try drinking it slower and see if the problem still continues. As for cold weather, I can only theorize that this can happen if you breathe through your mouth instead of your nose. If your nose is obstructed, reducing the nasal blockage may allow you to breathe through your nose.