When a toddler eats his or her own poop they are unlikely to get sick.
However if the toddler eats someone else's poop or a dogs or cats poop then they could get sick.
My brother when he was 2 years old would dig in his diaper and eat the poop and he turned out just fine and never got sick.
However he also started trying to eat cat poop but that could make him sick.
He's now 25 years old and is healthy so him eating his own poop never harmed him.
However it's best to stop the behavior when possible as it's still gross and a dirty habit that can spread bacteria from the toddlers hand to other surfaces etc.
It is normal for a toddler to eat their poop.
Just like it's also normal for a toddler to play with their poop but although it's normal for the toddler to eat their poop it needs to be stopped.
If the toddler is in diapers and digging the poop out of their diaper and eating it you need to watch the toddler more closely and change the toddlers poopy diaper before they have a chance to get to the poop.
Or put duct tape on the diaper all the way around it and put the toddler in footie pajamas such as the Little Keeper Sleeper so they have no access to their diaper and poop.
The toddler eating their own poop is unlikely to harm them but it's best to stop the habit as soon as possible because it is gross.
Eventually the toddler will outgrow the phase of eating their poop and playing with their poop though so that is good news.