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.