5 Key Ingredients in Seasonal Flu Shots

ingredients in flu shots

Vaccines can be a pretty controversial subject. And they have some nasty-sounding ingredients – formaldehyde, aluminum, mercury, even bits of dead flu. But love ’em or hate ’em, it’d be a good idea for all of us to learn more about the actual ingredients in flu shots. And about why they’re really there.

Deactivated Flu

Dead flu. Your immune system uses it to “make a pattern” of the virus. That way, the immune system will be able to recognize flu cells of this kind in the future and attack them. And since the flu changes every year, new “patterns” need to be made every year.

The viral ingredients in flu shots are deactivated, but the nasal spray version often uses live viruses weakened to the point where they’re harmless.


It’s an environmental pollutant and embalming chemical. But it’s in the vaccine for a good purpose – to make sure everything in there is dead. There’s only a tiny amount in the vaccine, not remotely enough to hurt us. After all, it’s there to kill viruses, not humans.


Aluminum salts are adjuvants. They ramp up your immune response. But many vaccines are aluminum-free. And the FDA makes the point that aluminum occurs naturally in most of our air and water.


This is the mercury-containing ingredient. But it’s ethylmercury, not the methylmercury you’d find in fish. And it’s only added to multi-dose vials. So if the syringes are one to a customer, they’re probably thimerosal-free. And you can request that as well.

Egg – Maybe

The flu viruses are grown in fertilized eggs. It’s possible some small amount of the egg made its way into the vaccine. Vaccines are usually safe for people with egg allergies, but it’s important to let your doctor know about them just in case.


There’s an old saying – the dose makes the poison. These are certainly tiny doses. And most ingredients in flu shots are already present in our bodies. But if you’re concerned, you might discuss it with your doctor.