Everybody's more prone to getting sick when chilly weather brings people – and their airborne, surface-clinging germs – closer together. But those with inflammatory types of arthritis, like rheumatoid arthritis, face added risk. That's because both the disease and certain therapies to treat it – like biologics and corticosteroids – interfere with the normal workings of the immune system, which offers protection from cold- and flu-causing viruses.

This also makes you more vulnerable to complications like pneumonia if you do fall ill, says Ruchi Jain, MD, an assistant clinical professor of rheumatology at Montefiore Medical Center in the Bronx, N.Y.

To build your defenses, brush up on cold- and flu-fighting know-how:

Myth or Truth?
Drinking water helps prevent sickness. 
Answer: Truth. Liquids can't flush away viruses, but they prevent dehydration, which can lead to overly dry nasal passages. Moist nasal passages are better able to fight off germy invaders. Nasal mists and nasal saline sprays add moisture, too.

Myth or Truth?
Zinc lessens cold symptoms.
Answer: Jury's out on this one. For every clinical trial that shows zinc – a mineral with antioxidant properties – shortens colds if begun within the first 24 hours of symptoms, another finds no such effects. If you do decide to try it, keep in mind that after five days of use, zinc lozenges can lead to mouth irritation, and after six weeks to copper deficiency. The FDA warns that zinc nasal sprays can cause permanent loss of smell.

Myth or Truth?
Echinacea fights colds.
Answer: Myth. While some studies show this herbal supplement reduces cold symptoms if started right away, three large studies funded by the National Center for Complementary and Alternative Medicine found no such benefit. Beware: Herbal supplements aren't standardized and can interact – or be mixed with compounds that interact – dangerously with arthritis drugs, Dr. Jain says. Consult your doctor before trying any supplements.

Myth or Truth?
To help prevent colds, walk in the sun.
Answer: Truth. Moderate physical activity, as well as getting plenty of vitamin D – which the body produces from exposure to ultraviolet rays from the sun – can help you fend off seasonal sickness. People who exercise regularly have fewer and milder colds, research shows. And some studies show people with reduced vitamin D have an increased risk of colds.

As an added bonus, both physical activity and vitamin D are associated with improving arthritis symptoms.

Myth or truth?
Loading up on vitamin C can ward off colds.
Answer: Myth. Dozens of studies have disproved this old saw for ordinary folks, although for some people in extreme conditions, like marathoners, taking 1,000 mg vitamin C regularly during cold season may slightly shorten colds.

Myth or truth?
You can catch a cold through your eyes.
Answer: Truth. Your eyes are connected to the nasal membranes by the tear ducts, allowing viruses to sneak in through your peepers. Rhinoviruses can live up to three hours on surfaces or on your skin – so hands off! Wash hands seven times a day or more – throughout the day – and you’ll cut your risk of respiratory illnesses in half, research shows. As effective alternatives, the Centers for Disease Control and Prevention, or CDC, recommends alcohol-based hand sanitizers or wipes. 

Myth or truth?
Flu shots are not safe if you have RA.
Answer: Myth. "People with autoimmune diseases are often afraid the flu vaccine will give them the flu or won't help," Dr. Jain says. "But it's safe and effective."

In fact, the CDC recommends an annual influenza vaccine for everyone with an autoimmune disease, unless they have an egg allergy (because the vaccine is made using eggs) or a history of serious side effects.

Those who take certain medications, like prednisone, may receive less protection, but it's still safer than going without, Dr. Jain says.

The flu shot won't give you the flu because it contains inactive virus. But people with autoimmune forms of arthritis or otherwise have compromised immune systems should avoid the nasal-spray version, which contains live virus.

What happens if you do get sick? For both the flu and colds, your best bet is to drop everything and rest, drink lots of fluids and tell your doctor. "Since your immunity is compromised already, it's smart to be more cautious and get health care early," says Dr. Jain. Your doctor may decide you need to back off certain medications, she says.

You may also want to take Tamiflu, a drug that eases flu symptoms; it’s safe for people with RA. But it must be started within two days of infection.