Your head’s stuffed up. Or maybe it’s your throat this time and your body aches like you were run over by a truck. What do you have? It could be this year’s flu, or a cold you picked up from the kids. It could be your seasonal allergies celebrating the rites of spring (or fall). You can learn to tell the difference between these by monitoring your symptoms. But once you learn what’s got you down, how do you know if you’re contagious?

The Flu

What is the flu?

The flu is a viral infection that targets your head and chest. You’ll have a runny or stuffy nose (sometimes both in the same day), watery eyes, probably a sore throat, and maybe a cough. As if that weren’t enough, your body will hurt, you’ll be tired, and you’ll probably run a fever over 100. You might feel those symptoms first, before respiratory symptoms develop. The flu will wipe you out — it’s not just a bad cold.

When is flu season?

Flu season typically starts in the fall and runs through the winter. A study published in the medical journal PLOS Pathogens suggested that flu viruses are most easily transmitted in winter, when the air is cold and dry.

For how long am I contagious?

The flu is contagious a day before and five days to a week after its onset.

Young children, people over 65, those with compromised immune systems, and people with a terminal illness are at risk of death from the flu. Pregnant women are also at greater risk. The flu can also cause premature birth.


What are colds?

Colds are viruses, too. There are many different viruses that can cause colds. They hit the respiratory system just like the flu, causing a runny or stuffed up nose, watery eyes, perhaps a sore throat, and sometimes a cough. You might get a low fever. Unlike the flu, colds come on slowly. Most people can feel themselves getting sick at least a day in advance.

When is cold season?

Colds tend to be more common in the fall and winter because that’s when people are indoors. The virus comes out in the droplets of sneezes and coughs. Those droplets land on a door knob or other public surface, and if you touch the surface and then touch your own eyes or nose, you can catch the cold too.

For how long am I contagious?

Colds are contagious from one day before you begin to experience symptoms until five to seven days after initially getting sick. You might develop a secondary infection like an earache that lasts longer than contagious symptoms.

Respiratory Allergies

What are respiratory allergies?

Your sneezing, sniffing, and watery eyes might not be due to a virus. You could have a respiratory allergy instead. These allergies are caused by irritants in your environment. Irritants include pollen, pet dander, dust mites, and mold. Respiratory allergies are referred to as rhinitis or good old hay fever. You won’t get a fever with allergies, though, just a lot of irritation. Your eyes can also be affected by allergies, a condition called allergic conjunctivitis.

When can I have allergies?

If your allergy is due to pollen, it’s a seasonal allergy. If you’re allergic to something you can encounter at any time, like pet dander, you have a perennial allergy.

How long am I contagious?

As you’ve probably guessed, allergies are not contagious.

Am I Contagious

When to Stay Home

If you have the flu

If you’ve determined that you have the flu, there’s only one thing to do: Stay in bed. You will probably lack the energy to do much else, and you can infect others if you are among them. Lie down, drink plenty of non-alcoholic, caffeine-free beverages, and wait it out.

You’ll probably want to return to work when your symptoms have abated somewhat, but you might still be contagious. To protect your coworkers, wash your hands rigorously and regularly. Warn others that you’ve been sick so they can remember to wash their hands. Sneeze or cough into your elbow, not your hands. You may also consider wearing a respiratory mask.

If you have a cold

Very few of us are able to stay home as long as colds last, but try to take a couple of days off. One of the reasons colds spread so easily is because while people might not feel great and are still contagious, they feel well enough to return to regular activities.

If you do go back to work during the contagious period, the same rules apply as if you had the flu: Wash your hands often, warn others, sneeze and cough into your elbow, and consider making yourself look silly with a mask that others will thank you for wearing.

If you have allergies

Allergies can certainly make you feel bad enough to call in sick. You won’t make anyone else sick if you go to work, though — just annoy them if your sniffling continues. That sniffling should diminish somewhat if you’ve moved away from the irritant, but effects can linger. There are prescription and over-the-counter medicines for allergies. If you’ve never had allergies before, ask your doctor for a skin or allergy blood test to learn what you’re allergic to.