The two main types of sinus infections are acute and chronic. In acute cases, symptoms typically last around two to four weeks, although cases are usually resolved in ten days. In cases of chronic sinus infections, symptoms can last for months and come on in recurrent episodes. Chronic sinusitis may be caused by allergies or environmental factors, such as exposure to smoke. It is considered normal to contract two sinus infections a year. However, any more than two sinus infections a year and a visit to an ears, nose and throat specialist is warranted. If left untreated, sinus infections can spread to other parts of the body. In the most severe case, the infection can spread to the blood, which causes a life-threatening condition known as sepsis.