If you break your leg, it should be able to heal just fine without any chemical assistance other than a good diet. But you might feel better if you also take some acetylsalicylic acid (aspirin).
Other health problems can benefit more from a chemist’s help. If you have a bacterial infection, some antibiotic chemicals that stop bacteria from growing, or kill the bacteria, might be a lot of help.
If you don’t get a balanced diet, or enough sun, then you might benefit from a chemist’s knowledge of vitamins and minerals.
Soap, toothpaste, acne medications, sunscreens, iodine, and chlorinated water all help keep you clean and free of infections.
But where chemistry really helps is when you have a serious health problem. Chemicals such as the insulin needed to treat diabetes, or the antivirals used to treat HIV are life savers. Drugs to treat cancer, heart disease, and stroke can prolong lives by years.
Knowledge of nutrition, which is the chemistry of what we eat, can also save lives and help people live longer.
On the other side of the coin, knowing which chemicals are dangerous can also save lives. The chemistry of poisonous substances (toxicology) helps keep us safe, but it also helps to control pests that can affect our health, such as mosquitoes, rats and mice, cockroaches, and flies. Pesticides also increase crop yields, allowing more people to get the nutrition they need.