You’re feeling pretty lousy. You’ve got sniffles, sneezing and a sore throat. Is it a cold, flu or allergies? It can be hard to tell them apart because they share so many symptoms. But understanding the differences will help you choose the best treatment.

Cold, flu, and allergy all affect your respiratory system, which can make it hard to breathe. Each condition has key symptoms that set them apart.

Colds and flu are caused by different viruses and the symptoms associated with the flu are more severe. Both illnesses can lead to a runny, stuffy nose; congestion; cough; and sore throat. But the flu can also cause high fever that lasts for 3-4 days, along with a headache, fatigue and general aches and pain. These symptoms are less common when you have a cold.

Allergies are a little different, because they aren’t caused by a virus. Instead, it’s your body’s immune system reacting to a trigger, or allergen, which is something you’re allergic to. If you have allergies and breathe in things like pollen or pet dander, the immune cells in your nose and airways may overreact to these harmless substances. Your delicate respiratory tissues may then swell, and your nose may become stuffed up or runny.

Allergies can also cause itchy, watery eyes, which you don’t normally have with a cold or flu. Allergy symptoms usually last as long as you’re exposed to the allergen, which may be about six weeks during pollen seasons in the spring, summer or fall. Colds and flu rarely last beyond two weeks.

Most people with a cold or flu recover on their own without medical care. But check with a health care provider if symptoms last beyond 10 days or if symptoms aren’t relieved by over-the-counter medicines.

To treat colds or flu, get plenty of rest and drink lots of fluids. If you have the flu, pain relievers such as aspirin, acetaminophen or ibuprofen can reduce fever or aches. Allergies can be treated with antihistamines or decongestants.

Be careful to avoid “drug overlap” when taking medicines that list two or more active ingredients on the label. For example, if you take two different drugs that contain acetaminophen — one for a stuffy nose and the other for headache — you may be getting too much acetaminophen.

Read medicine labels carefully — including warnings, side effects, dosages. If you have questions, talk to your doctor or pharmacist.