It's irritating when you think you are doing something healthy for yourself & it ends up with this kind of reaction.

Could be they hit the muscle wrong since theybare IM (inter muscular) shots, or hit a nerve.....or it could be a reaction to either what it's mixed with or the flu viruses themselves.

The flu virus is inactivated (not a live virus) so as not to cause the flu. Many flu vaccines have the virus grown inside fertilized chicken eggs or in animal cells (newer Flucelvax vaccine).

Preservatives which can cause reactions are thimerosal (protecting against bacteria & fungi)..it contains mercury at a small dose they say isn't toxic at that dose....can get thimerosal-free version.

Stabilizers Sucrose (table sugar), sorbitol (artificial sweetener), & MSG (mono sodium glutamate - flavor enhancer) keep the vaccines stable....keep them from losing potency even when exposed to heat or light. They claim the amounts are too small to have any effect (ya, ya)

Antibiotics neomycin, gentamicin or others to stop bacteria from contaminating the vaccine.

Polysorbate 80 an emulsifier that keeps all ingredients evenly distributed.

Formaldehyde used to inactivate the virus toxins..mostly removed but trace levels remain supposedly many times lower than what is naturally(?) found in the human body.

Serious side effects are:
Trouble breathing or wheezing
Swelling of eyes lips or tongue (one of my allergic reactions to an antibiotic was swollen tongue)
Hives
Weakness
Fast heartbeat
Dizziness

Mild reactions are considered to be
Tenderness, redness, swelling around the shot location
Fever
Fatigue
Headache
(dang, I wouldn't accept the last 3 especially as being ok either)