The latest strike will run from Monday 9 September to Friday 13 September inclusively - and will be on the top of the 17 days already taken or scheduled.
The dispute centres on Unite's contention that its 58 members in Lincolnshire have lost more than £2,000 a year since they were transferred under Agenda for Change terms from the NHS to Lincolnshire County Council in October 2017.
The union also argues that an erosion of professional responsibilities, with fewer staff doing the specialist health visitor role, will hurt vulnerable families.
Sending my solidarity to the striking health visitors in Lincoln today.— Jeremy Corbyn (@jeremycorbyn) August 17, 2019
Labour will always stand up for all our health workers, and ensure that they get the support they deserve.
When polled, the health visitors voted by an 84 per cent majority to strike.
It is thought that this is the first time that the county's health visitors have taken strike action in defence of their pay and professional standards.
Unite regional officer Steve Syson said: "The Conservative-led council's treatment of these employees takes the biscuit, especially at a time when the number of health visitors in England is at the lowest level since September 2009.
"These dedicated employees have been denied cost of living rises since October 2017, even though other council employees have received pay awards in that period.
"Ironically, if the health visitors had remained in the NHS, which was their wish, they would have received pay awards.
"To compound this, the council is failing in its public duty to resolve this issue and is adamantly refusing to consider reasonable proposals from Unite, while allowing the families in Lincolnshire, many of whom are in vulnerable circumstances, to suffer from a depleted service."
But Lincolnshire County Council continue to dispute Unite's claims.
Heather Sandy, interim director of education at the council, said they do not consider the union's proposals to be reasonable.
"The council is disappointed that Unite, who represent about a third of the health visiting workforce, have continually failed to engage with our collective disputes procedure and took the step of balloting for industrial action," said Sandy.
"However, we have engaged with constructive dialogue with representatives from Unite with the assistance of ACAS in an attempt to resolve their dispute.
"We remain committed to moving ahead with career progression plans for our health visitor workforce, which is the mechanism to receive pay increases over and above what the NHS are paying.
"We have written to staff explaining how the scheme will work and how it offers salaries beyond those available in the NHS. All health visitors who successfully progress through the scheme will benefit in this way."
Sandy added that there is no evidence that health visiting services will be affected by the strike, with only an average of 12 health visitors per day taking action.
"If further strikes go ahead, we have plans in place to cover absences, particularly in the most vulnerable areas such as safeguarding and primary birth visits.
"Again, the picture portrayed by Unite about health visitor numbers is wrong.
"In Lincolnshire the number of health visitors has actually increased since the service moved to the council following more investment in support for families with young children. This is against the national trend."