Every winter, families must defend their homes against invisible invaders — cold germs and flu viruses.

But staying cold-and-flu-free through the winter can prove a losing battle. Sure, you enforce hand washing and elbow-coughing at home, but all you need is for one child to get sick at school — the next thing you know, your entire family’s ill.

So what’s the best way to protect your family from illness this winter? Sometimes cliches do ring true — the best offense is good defense. Boosting your family member’s immune systems will better equip them to evade colds and flu.

Pharma Care, a company that specializes in immune-boosting products, offers the following tips for families hoping to naturally avoid catching colds and flu this winter:

Wash your hands, and keep your hands away from your face. Washing your hands really is the best defense against cold and flu. Most germs are spread through direct contact or when a sick person touches an object and then a healthy person handles that same object, picking up germs on their hands. Wash your hands thoroughly and often, and don’t touch your face — cold and flu viruses enter your body through the eyes, nose or mouth. Use a hand sanitizer after wiping a child’s runny nose.

Give your immune system what it needs. Eat plenty of fresh fruits and vegetables — they contain vitamins and antioxidants, which will help your immune system stay strong.

You should also consider taking an immune-boosting supplement. Try Sambucol, an elderberry extract, which contains high concentrations of flavanoids, powerful antioxidants that help support immune function. Sambucol also offers a kids’ version, so you can improve the health of your whole family.

Stay active. It might be hard to believe, but going out in cold weather may help you avoid illness. If you stay indoors, you will be in closer contact with more people, a situation that allows germs to circulate. Central heating, too, can dry out nasal passages, leaving you more vulnerable to infection.

Try taking the kids skiing or sledding. Even shoveling or building snowmen can provide exercise. Studies show that aerobic activity improves immune function and reduces stress, another factor that can increase your chances of catching colds or flu.