Messages that ignore harms

Don’t assume there are no harmful effects of a health action.

We often think about the benefits of doing something for our health and ignore possible harms. But few treatments that work are 100% safe.


People often think about the good things that a health action, like acting on health advice, can do, and sometimes don’t think about how a health action might also cause harm. Harms may also be called “unwanted effects”, “side effects” or “adverse effects”. In fact, very few health actions that help are harmless (100% safe). Even simple advice can sometimes cause harm. So, be careful if someone says that doing something is “100% safe” or doesn’t mention its safety or downsides.


In many countries, health professionals told people that babies should sleep on their tummies, so they would not choke if they vomited. This included Benjamin Spock, an influential American child health expert, who in his bestselling book Baby and Child Care, advised millions of readers to put babies to sleep on their tummies. But then researchers found that babies who had died of unexplained causes were three times more likely to have been sleeping on their tummies. After this, the advice was changed to put babies to sleep on their backs. However, if the advice had been updated earlier, it might have saved the lives of more than 50,000 babies.

Remember: Always consider the possibility of harmful effects, not just helpful effects.

Educational resources for this concept

Primary school resources


Secondary school resources




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