A Dunedin essential worker found silicon smeared over her windscreen, leaving her unable to work.

That worker, who declined to be named over fears of further retribution, believes a resident may have been concerned she was making unnecessary trips.

But her trips were essential.

The 52-year-old is a carer who travels to look after elderly residents living in their own homes, that includes helping them with medication, taking them for works, and shopping for groceries.

She was heading to one of those homes when she noticed the unusual smear across the windscreen of her car, which was parked on a quiet street in the suburb of Shiel Hill.

Attempts to remove the smear, which a friend later identified as a silicon spray, only made it worse.

The woman had to tell her employer she could not work.

Her friend told Stuff he was initially concerned the windscreen would need to be replaced, as it "becomes instantly fogged as soon as she drives despite her best efforts at removing the oily, sticky coating".

After being advised by a glass specialist to use a mineral turpentine, it was removed.

The friend described it as a "rotten act".

"What this idiot probably failed to realise is that she is a essential support worker providing in home care for the elderly."

The victim believed someone in the neighbourhood, annoyed that she would depart her home at various times during the lockdown, engaged in vigilantism.

"They were probably watching my comings and goings."

She had a simple message for them.

"It is important to get your facts rights before acting."

Police confirmed they were investigating.