There are thousands of online health resources, and new ones seem to crop up every day. They’ve become important and trusted sources of health information for many people. While some are useful, others can be misleading or inaccurate.

Aside from that, there are many medical beliefs we’ve gathered through the years—some so ingrained that we believe them to be true, without question. Some are things our mothers and their mothers told us; others are hearsay. Here are a few and some info that debunks them.

1. You must drink 8 glasses of water a day.

There is no scientific evidence to support this recommendation. For most people, thirst is the best indicator of how much water our bodies need. And it’s not only water that counts as hydration: so do tea, juice, milk, coffee, fruits, vegetables and other foods and beverages. (Coffee is not a diuretic, as some people think.) Urine is generally a good indicator if you’re drinking enough—if it’s dark yellow, you probably need to drink more.

2. You catch a cold from being cold (or going out with wet hair).

Being out in the cold cannot cause you to catch a cold. A cold is caused by a virus; you’re more likely to catch a virus when you’re indoors, where viruses can breed and germs are more easily spread.

3. Reading in dim light will ruin your eyesight.

The health and function of your eyes will not be altered by reading in low light. What it can do is cause temporary eyestrain, so it’s best to blink more often if your eyes feel tired to keep them moist and keep away dust. And rest your eyes every 20 minutes or so to give them a break.

4. If you’re getting hot flashes, you must be in menopause.

Yes, these heat surges are commonly caused by perimenopause and menopause, but there are other reasons you might get them, ranging from stress, anxiety, wine, certain prescription drugs, excess weight, food allergies or sensitivities and certain medical conditions like thyroid issues.

5. If you don’t have a family history of breast cancer, you don’t have to worry.

Most cases of breast cancer are not caused by heredity; in fact, only 5 percent to 10 percent of breast cancers are believed to be inherited and caused by abnormal genes passed from mothers or fathers to the child. (Another common myth: Breast cancer is only inherited from your mother’s side.) To lower your risk, watch your weight, avoid diets high in fat, limit alcohol consumption and get plenty of physical activity.