5. Sinus Problems
The sense of smell is very closely interlinked with that of taste, so a sinus problem can result in a bad taste in the mouth. As the sinuses are linked to the back of the mouth, any infection in them can affect the mouth and subsequently the sense of taste. Conditions such as allergies, colds and flu, sinusitis, hay fever and upper respiratory tract infections can all have an effect on your sense of taste, causing a metallic taste in your mouth. Fortunately this will disappear as soon as the sinus problem is cleared up.