Diphtheria signs and symptoms usually begin 2 to 5 days after a person becomes infected. Signs and symptoms may include: a thick, gray membrane covering the throat and tonsils, sore throat and hoarseness, swollen glands (enlarged lymph nodes) in the neck, difficulty breathing or rapid breathing, runny nose, fever and chills with fatigue.

In some people, infection with the bacteria that cause diphtheria results in only a mild illness or shows no noticeable signs and symptoms. Infected persons who remain unaware of their illness are known as diphtheria carriers. They are called carriers because they can spread the infection without becoming ill themselves. Diphtheria can also cause some symptoms on the skin. Affecting the skin, it can cause pain, redness and swelling, similar to other bacterial skin infections. Ulcers may also develop on the skin. It may occur particularly in people living in crowded conditions with poor hygiene.