Cold vs. Flu vs. Allergies: How to Tell Them Apart

Colds, flu, and allergies can all start with a stuffy nose and a scratchy throat, which is why so many people reach for the wrong remedy. The fastest way to tell them apart is speed of onset and the presence of fever.

Colds build gradually over a day or two, rarely cause a high fever in adults, and usually clear up within seven to ten days. Flu symptoms hit hard and fast — often within hours — and commonly include a fever above 100.4°F, body aches, and fatigue that colds don’t typically cause.

Allergies are the outlier: no fever, ever. Look for itchy or watery eyes and symptoms that flare in specific settings (spring pollen, a dusty attic, a friend’s cat) and can last for weeks as long as you’re exposed to the trigger.

A simple rule of thumb: fever points toward flu, itchy eyes point toward allergies, and everything in between — mild, gradual, no fever — is probably a common cold. If symptoms are severe, don’t improve after 10 days, or you’re in a high-risk group, check in with a healthcare provider rather than self-treating indefinitely.